An unclose shot of a stack of 8 steamed buns on a white ceramic plate. There is one half of a steamed bun at the top of the pile, split in half, revealing its yellow-orange egg yolk lava filling.

Salted Egg Yolk Custard Buns (Liusha Bao)

Soft and fluffy steamed buns, filled with a sweet molten lava-like egg yolk center. I first discovered these salted egg yolk custard buns at a dim sum restaurant during our family’s weekly Saturday morning tradition when I was a child. My bun even had a cute pig face that oozed when squeezed. I couldn’t wait for it to cool down and took a bite, almost burning my lip. The rich, sweet, buttery egg yolk filling was instantly satisfying. These buns are special because of their richness, owing to the use of salted duck egg yolks. This can make them a bit costly to buy pre-made. With this recipe, you can have dim sum anytime from the comfort of your home!

An unclose shot of a stack of 8 steamed buns on a white ceramic plate. There is one half of a steamed bun at the top of the pile, split in half, revealing its yellow-orange egg yolk lava filling.

What are steamed buns?

Originating in ancient China, steamed buns (known as mantou, milk buns, baozi, or bao) have a long history spanning thousands of years. Today, they are savored far beyond Asia, including in countries like Germany, Poland, America, and Africa. My steamed buns consist of flour, yeast, and milk. While some regional recipes may incorporate oil, sugar, and salt, I prefer to omit these extras as I find them unnecessary. Steamed buns showcase remarkable versatility, available plain, filled with sweet pastes, or featuring savory fillings like vegetables or meat.

What are salted egg yolk custard buns?

In Chinese, we call salted egg yolk custard buns liusha bao (流沙包), which directly translates to flowing sand bun. This phrase essentially refers to a custard bun or a bun filled with salted egg yolk custard. These buns consist of a dough made from ingredients like yeast, milk, or water, and they are filled with a molten mixture composed of salted duck egg yolks, milk or custard powder, sugar, and butter. Afterward, these buns undergo proofing and steaming, transforming from dough into fluffy and airy bread. The use of melted butter contributes to the filling’s ability to flow like lava. If you like this recipe, you may also like: Custard Buns, Pork Buns (Cha Siu Bao), Red Bean Buns, and Steamed Buns (Mantou).

What do salted egg yolk custard buns taste like?

Steamed buns have an airy, light, and subtly sweet texture, while the lava filling offers a sweet, creamy, buttery consistency with a subtle graininess due to finely ground egg yolks. The salted duck egg yolks provide a distinct umami-rich, eggy flavor, making these buns especially appealing.

A stack of 8 steamed buns on a white ceramic plate. One of the steamed buns is split in half, revealing its yellow-orange egg yolk lava filling.

Why This Works

Steamed buns might seem challenging to make because we typically associate bread with baking, but in reality, they involve straightforward techniques like kneading and steaming. In my steamed buns recipe, I use chilled milk combined with yeast and all-purpose flour. This technique results in softer and slightly sweeter steamed buns. The chilled milk contributes to a tender texture, while the addition of yeast enables the dough to rise and become fluffy. The sweetness of the buns is determined by its lactose content which is why I recommend using whole milk over other varieties. If you’re someone who prefers a sweeter dough, you can up to three tablespoons of sugar to it.

This recipe is versatile and accommodates different approaches to kneading the dough. You can opt to knead the dough by hand for 15 minutes, or alternatively, use a stand mixer with a dough hook for 10 minutes on high speed. Both methods yield excellent results, making it easy for you to choose the option that best suits your preferences and available equipment.

Achieving the perfect texture in salted egg yolk custard buns is all about having the right formula. I’ve conducted thorough testing of my lava bun recipe to ensure that both the technique and texture come out just right. The filling is specially formulated to be easily shaped into a ball while maintaining a molten lava-like flow.

What kinds of fillings are suitable for steamed buns?

In Chinese cuisine, the most commonly used fillings for steamed buns are red bean, black sesame, vegetable, salted egg yolk custard, chasiu (Chinese barbecue pork) or ground pork. When selecting a filling, it is important to choose one that is soft to firm in texture but not runny.

You can find sweet pastes at a Chinese grocery store or through online Chinese grocery retailers. Look for them in the dry pantry aisle or refrigerated section; I have found them in both places at various supermarkets. Steamed buns are not just popular in Chinese cuisine; they are also widely enjoyed in Filipino, Malaysian, Indonesian, Japanese and Vietnamese cuisines. You may be able to find the fillings at specific grocery stores that cater to these cuisines as well but I have not personally checked there.

The special ingredients needed to make sesame balls from top left to bottom, glutinous rice flour, white sesame seeds, black sesame seeds, black sesame paste, taro paste, lotus seed paste, red bean paste

What if I want steamed buns without filling?

For steamed buns without any filling, you can refer to my Steamed Buns (Mantou) recipe! 

Can I store steamed buns for later?

For optimal appearance and to maintain a lava-like texture, it is best to consume leftover salted egg yolk custard buns on the same day. Although they will still taste the same, methods such as microwaving can further cook the filling, leading to dryness and a loss of the desired lava-like texture.

If you happen to have leftover buns or wish to prepare them in advance, freezing is a great option. After allowing the buns to cool to room temperature, making sure to separate them to prevent them from freezing together. Then store them in an airtight container or use a freezer-safe ziplock bag. This ensures they maintain their freshness and prevents freezer burn, preserving their taste when you’re ready to enjoy them later.

How do I reheat steamed buns?

Reheating frozen steamed buns is a breeze, and you have two options, with or without a steamer. Both methods do not require the buns to be thawed first. For the microwave method, simply wrap each frozen bun individually in a water-soaked paper towel and microwave them for 30 seconds at a time. My microwave usually take 45 seconds. This quick and easy method works perfectly for both filled and unfilled buns, ensuring they become warm, soft, and ready to enjoy in no time!


What are salted duck egg yolks?

If you’ve ever enjoyed a mooncake, you’ve likely tasted salted duck egg yolks before. These yolks play a pivotal role in mooncakes, traditional Chinese pastries are closely linked to the Mid-Autumn Festival. They are considered a luxury ingredient, contributing to the premium cost of mooncakes that contain them. Despite their name, they are not salty but cured. Salted duck egg yolks are crafted by coating duck eggs with a salt mixture, then patiently curing them for several months until they reach the desired readiness for cracking. Through this meticulous curing process, these yolks develop their distinctive vibrant orange or golden hue.

Where can I purchase salted duck egg yolks?

Salted duck egg yolks are a Chinese product readily available at Chinese grocery stores. You can typically find them in an either the freezer or refrigerated section. Personally, I prefer duck eggs with clear yolks rather than cloudy ones. Choose duck egg yolks that are vacuum sealed for freshness. A package of duck eggs typically includes 12 to 20 salted duck eggs and is priced at approximately $7 USD per bag.

Can I substitute out the salted duck egg yolks?

Please refrain from making substitutions to the salted duck egg yolks, which are a crucial ingredient that makes this recipe authentic. Substituting them with regular chicken egg yolks or homemade cured chicken egg yolks will alter the flavor and texture of the dish.

The ingredients required to make the filling for lava buns from top left to bottom right: unsalted butter, sugar, water, salted duck egg yolks, gelatin powder, milk powder, and cornstarch
The ingredients required to make the filling for salted egg yolk custard buns from top left to bottom right: unsalted butter, sugar, water, salted duck egg yolks, gelatin powder, milk powder, and cornstarch

Is the gelatin necessary?

Yes, adding gelatin powder to the lava bao filling is important. It gives the filling firmness and malleability, making it easy for you to shape into balls. The gelatin also keeps the filling intact before steaming, preventing the buns from collapsing or breaking. From my personal experience, it enhances the texture and simplifies the bun-making process. You can find gelatin powder in most grocery stores. I use the Knox brand, which comes in a small box containing three packets, each with slightly over two teaspoons of gelatin powder.

Which type of flour is required to make steamed buns?

Before making this recipe, you need to be aware of the type of flour required. Flour plays a crucial role in creating the structure and texture of your buns. Using flour with insufficient gluten can lead to shrinking or collapsing buns. To avoid dough shrinking, opt for bleached all-purpose flour. I am using Gold Medal Bleached All Purpose Flour. It’s important to note that even though it is labeled as “bleached,” your buns will still have a slightly off-white yellow color.

In Chinese/Vietnamese stores, you may come across special “bot bao flours” specifically designed for homemade steamed buns. These flours differ from regular all-purpose flour as they undergo extensive bleaching, resulting in a whiter appearance. While they may appear more visually appealing, they often lack flavor and sufficient gluten content to provide the necessary structure for well-formed steamed buns. It’s also worth noting that these specialized flours can be more expensive than all-purpose flour.

Can I use a gluten free flour?

If you have gluten intolerance, gluten-free flours will not be suitable for this recipe. ): However, you might be interested in my Sesame Balls recipe which uses glutinous rice (sticky rice) flour which aligns with your dietary requirements.

Can I substitute out the whole milk?

For the best results in my steamed bun recipe, I highly recommend using whole milk. It plays a significant role in the recipe, providing a natural sweetness without the need for additional sugar or milk. It also helps to create a light, airy, and fluffy texture. Substituting with other types of milk, especially plant-based ones, may alter the flavor and texture of the buns, so I advise against making any substitutions in this particular case. For those concerned about whole milk’s fat content, it’s essential to note that whole milk actually contains only 3.25% milk fat.

What if I am lactose intolerant?

However, if you’re lactose intolerant, feel free to use chilled water instead of plant milks. Plant milks often have added sugar and flavorings, among other things, which could affect the outcome of the buns. Water will yield the most consistent results in this situation. Just be aware that doughs made with water may taste somewhat bland due to the absence of lactose, which is a natural sugar present in cow’s milk.

What is yeast?

Yeast is a type of fungus that is commonly used in baking. It consumes the sugars in the milk and flour and then releases carbon dioxide gas, which causes the dough to rise. Yeast can be found in two forms, fresh or dry. When used in baking, yeast helps to create a light and airy texture in breads and other baked goods. Here are the different types of yeast available:

  • Dry – This type of yeast is more commonly found sold in a small envelope at grocery stores, supermarkets, and online retailers. It can be stored in the pantry for several years, but it’s best to use it within 3 months of purchase.
    • Active Dry – Needs to be dissolved in liquid (slightly warm water or milk) before using
    • Instant (rapid-rise yeast, bread machine yeast) – Can be added directly to dry ingredients without proofing. It is finer and more active than active dry yeast.
  • Fresh (compressed yeast) – This type is perishable and must be stored in the refrigerator. It can be found at some specialty food stores, but its availability may vary. It is typically sold in large blocks, which may be more than is needed for everyday home baking. This type of yeast is typically used by professional bakers, it has a shorter shelf life than dry yeast and should be used quickly after purchase. It also can be found in smaller portions, but it’s best to check the availability at local specialty food stores or bakeries.

For steamed buns, my preferred choice is active dry yeast. I recommend purchasing it in dark jars from the refrigerated section.

How do I buy dry yeast?

Active dry yeast is available at most grocery stores or can be easily ordered through grocery delivery apps, making it easily accessible. When choosing your yeast packaging, I recommend opting for jars instead of individual envelopes. Jars provide greater shelf stability and reliability for long-term storage.

To guarantee the best performance, pay close attention to the yeast’s expiration date, as its effectiveness diminishes over time. For optimal results, use the yeast within 3 months of purchase and dispose of any that has been sitting in the pantry for an unspecified duration.

Proper storage is key to preserving the yeast’s potency. Keep it in a cool, dry place, away from direct light and moisture, to maintain its activity and ensure your baked goods rise flawlessly. Following these guidelines will help you achieve fantastic results in your baking endeavors with active dry yeast.

How do I test if my yeast is still alive?

Yeast is a living organism so ensuring that it is active before using it in a recipe is essential. To do this, you can perform a simple test: Mix the yeast with a tablespoon of liquid, like milk or water, and wait for 5 minutes. If it becomes frothy and bubbly, the yeast is active and ready to use. However, if there is no change, it indicates the yeast is no longer alive and should be discarded.

When working with yeast, it’s crucial to use chilled or lukewarm liquid to prevent heat from exceeding 115°F / 65°C, which could kill the yeast. Though not always mentioned in recipe instructions, checking the yeast’s activity is a good practice to ensure successful bread-making.


What is parchment paper and what can I substitute it with?

Parchment paper is most often used in baking. Even if you did not bake them yourself you probably have seen cookies on a baking tray. Parchment paper has non-stick properties making it a perfect option for steaming buns with which is a food that is quite sticky especially when it makes contact with water. You’ll find parchment paper in various varieties, and while some may come pre-cut, I’m here to show you that anyone can easily make it fit in their steamers by cutting a whole sheet. If you don’t have parchment paper, don’t sweat it! (let the buns do the sweating) You can use cupcake liners, Napa cabbage leaves, or banana leaves.

Do I need a stand mixer for this recipe?

Kneading the dough is an essential step in this recipe because it achieves smoother buns. The easiest and most time-effective method is by using a stand mixer with a dough hook. This beats the dough until it’s smooth and supple in only 10 minutes. If you prefer, you can knead the dough with your palms for approximately 15 minutes, which also doubles as a great workout!

What type of steamer do I need?

There are several types of steamers that can be used to cook steamed buns. Here are my recommendations from most recommended to least:

  • Steamer Inserts: These fit into most pots and pans, making them a versatile choice for steaming various dishes. They are easy to use and maintain.
    • Bamboo Steamer: If you have ever dined at a dim sum restaurant, you have most likely seen this before. It is an affordable choice in Chinese cuisine. It is made with bamboo trays with a lid on top that can be layered and stacked with more trays. The steam rises from the boiling water in the bottom pot and cooks the buns placed in the trays above. These steamers are the most efficient as they excel in trapping the majority of the steam, allowing minimal escape.
    • Metal Steamer Insert: A metal steamer insert is a kitchen tool made of stainless steel, designed to fit inside a pot, pan, or rice cooker. It’s used for steaming food, like vegetables. The insert has small holes to allow steam through, can be used for various foods, and is easy to clean.
  • Tiered Metal Steamer Pot: Similar to bamboo steamers, metal tiered steamers consist of stacked metal trays with a lid. They work in the same way as bamboo steamers but offer the advantage of being more durable and easier to clean.Tiered metal steamer pots, while not space-saving due to their bulkiness, are exceptionally durable and can last a lifetime.
  • Improvised Steamer: If you don’t have a dedicated steamer, you can create an improvised steamer using a large pot with a tight-fitting lid and a heatproof wire rack or a few heatproof bowls. Place a small amount of water in the pot, set the heatproof rack or dishes above the water level, and cover the pot with the lid.
    • Cons
      • Limited space: The improvised steamer setup may have limited space, making it challenging to steam larger quantities of food at once.
      • Inconsistent results: Without precise control over the steaming process, you may experience inconsistency in the texture and doneness of your food.
      • Limited capacity: The size of the steamer insert may limit the quantity of food you can steam at once, especially for larger gatherings or meals.

How do I steam buns?

Set up a steamer over the stove and add water according to the type of pan you’re using. For metal steamers or steamer baskets, typically, 1 cup of water is sufficient. However, if you’re using a larger pan or a bamboo steamer, you may need to adjust and add more water. Ensure the water level is below the wire of the steamer basket, colander, or wire rack, so it doesn’t touch the buns during steaming, which could make them soggy.

Cover the steamer with a lid and allow the buns to proof until they have doubled in size. In warmer climates, this may take about 1 hour, while in colder climates, it could take up to 2 hours. Once proofed, steam the buns, and they will double in size again during the steaming process. Once the dough balls are shaped and transferred onto parchment paper, place them in the steamer basket, ensuring they are spaced approximately 1 inch apart from each other.

An overhead view of six white steamed lava buns arranged on parchment paper inside a steamer/colander, positioned in an uncovered pan. The buns are slightly touching, indicating their expansion during proofing and steaming, with a smooth texture.


Why isn’t my dough ball smooth?

To achieve the best texture, knead the dough by hand for 12-15 minutes, or half the time with a stand mixer using a dough hook. Based on my experience, the dough hook produces excellent results.

To make sure that there is enough moisture for the dry ingredients, I recommend using a scale instead of using measuring cups. Cup measurements may vary if the ingredients are packed or sifted, leading to inconsistencies. When using measuring cups and spoons, ensure to level off the ingredients for closer accuracy. Cooking with a scale is simple, requiring only a bowl, a scale, and a tool to transfer the ingredients.

Why did my salted egg yolk custard buns collapse?

If your salted egg yolk custard buns collapsed during the resting stage, it’s possible that the filling was not fully frozen. Ensure that the filling is frozen until it’s completely firm before incorporating it into the steamed bun dough. Additionally, avoid opening the lid of the steamer or pan during the steaming process. Allow the buns steam undisturbed for the entire recommended time to maintain proper rising and structure. Before steaming, ensure you allow enough time for the buns to “proof,” allowing the dough to rise for about 1-1.5 hours. This step helps the dough rise and develop a protective outer layer.

An unclose shot of a stack of 8 steamed buns on a white ceramic plate. There is one half of a steamed bun at the top of the pile, split in half, revealing its yellow-orange egg yolk lava filling.

Egg Yolk Custard Buns

Soft and airy steamed buns, brimming with a sweet molten lava filling.
Prep Time 10 minutes
Cook Time 15 minutes
Refrigeration and Proofing Time 3 hours
Total Time 3 hours 25 minutes
Course Breakfast, Dessert
Cuisine Asian, Chinese


  • Pan with a Steamer Basket
  • Cutting Board
  • Food Processor or Knife
  • Bowl
  • Rolling Pin
  • Steamer
  • Parchment Paper



  • 12 salted duck egg yolks
  • 3/4 cup sugar
  • 2 tbsp dry milk powder
  • 2 tsp unflavored gelatine
  • 2 tbsp cornstarch
  • Slightly under 1/2 cup water
  • 1/4 cup and 3 tbsp unsalted butter


  • 3/4 cup whole milk chilled
  • 1 tsp active dry yeast
  • 2 cups all purpose flour


  • Prep | Place a pan on the stove with a steamer basket. Fill the pan with enough water for steaming. Bring the water to a boil.
    Add in the salted egg yolks. Cover with a lid and steam for 10 minutes over medium heat. Transfer the steamed salted egg yolks onto a cutting board and allow them to cool.
  • Filling | Finely mash the yolks using a food processor on low speed for 10 seconds or using the back of a knife to mash.
    In a bowl, mix the sugar, milk powder, gelatin, and cornstarch.
    Empty the pan and return it to the stove, setting it to medium heat. Add water and the sugar mixture to the pan and stir until boiling. Add the butter into the mixture and stir until it melts. Add in the ground salted egg yolks, and stir.
    Transfer the filling into a bowl and chill in the refrigerator until firm. Divide into 8 pieces and roll into balls. Cover with a lid and freeze until hardened.
  • Dough | Prepare a portion of my steamed buns dough. Mix together chilled milk and yeast. Add the flour and stir with a spatula until the mixture becomes clumpy.
    Use your hands to knead the dough for about 15 mins. If you’re using a stand mixer with a dough hook, mix for 10 mins. Initially, the dough may feel sticky, but as you knead, it should become smooth. 
    Cover the dough ball with plastic wrap or a lint-free towel and let it rest for 5 minutes.
  • Shape | Divide the dough into 8 pieces. Take one piece, roll it into an oval with a rolling pin.
    Fold the top half to the middle and seal. Fold the bottom half to the middle. Pinch opposite edges to form a ball.
    Roll the dough ball into a 1/2 inch thick, 4 inch wide circle. Be sure to keep the center thicker than the edges.
  • Fill | Place a scoop of frozen filling in the center flat side up. Pinch opposite edges and shape into a sphere. Twist to seal. Repeat with the remaining ingredients.
  • Steam | Place the buns into the basket of a steamer smooth side up on parchment paper. Space them at least one inch apart to allow them to expand. You may also steam them in batches. Repeat.
    Cover with a lid and rest for 1 hr until doubled in size. Steam on high heat for 15 mins. Serve warm.
    If you've tried this recipe, please let me know what you think in the comments below! Your feedback is greatly appreciated and it helps me improve my recipes for future cooking adventures. And if you enjoyed it, don't forget to give it a thumbs up or share it with your friends! You can help my channel by tagging @vocabularyoffood in your cooks. ۶(◠ 。◠)۶
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