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!

What are steamed buns?

Originating in ancient China, steamed buns, known as mantou, milk buns, baozi, or bao, have a history spanning thousands of years. Today, they appear far beyond Asia, in places across the globe, from Germany and Poland to America and Africa. What truly sets steamed buns apart is their versatility. They can be enjoyed as is or filled with sweet pastes or savory fillings, like vegetables or meat. Whether you enjoy them as a meal, a side dish, or a quick snack, steamed buns cater to a wide range of preferences. They can also range in size from mini to extra-large. Unlike American dinner rolls which contain butter and eggs, my steamed buns are composed of only flour, yeast, and milk. Most importantly, they are traditionally steamed in a bamboo steamer rather than being baked in an oven, which is the secret behind their exceptionally soft and fluffy texture.

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.

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 just 10 minutes. 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. If this recipe interests you, you may also like: Pork Buns (Cha Siu Bao), Red Bean Buns, Custard Bun, Sesame Balls, Shumai (Shaomai, Siumai), and Chicken Dumplings.

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.

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!

Ingredients

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.

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.

Equipment

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

Parchment paper is primarily associated with baking, and it’s a common sight to see cookies arranged on a baking tray lined with it. Parchment paper’s non-stick characteristics make it an excellent choice for steaming buns as well. You can find parchment paper in various forms, and some may even come pre-cut for convenience. If you don’t have it on hand, don’t worry (let the buns do the sweating!). There are alternative options available. You can use cupcake liners, air fryer basket liners, or even Napa cabbage as substitutes.

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. In my original steamed buns recipe video, I’m showcasing a versatile pan that does come with a convenient steamer basket. While it may seem like a great all-in-one solution, it’s important to consider some drawbacks when using this pan for steaming. One of the primary concerns is the difficulty in gauging water levels within the pan. This limitation poses a real risk of overheating, potentially resulting in burnt food and, ultimately, permanent staining of the pan.

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.

Troubleshooting

Why isn’t my dough ball smooth?

To achieve the best texture, knead the dough by hand for 15 minutes, or for a minimum of 10 minutes with a stand mixer using a dough hook. Based on my experience, the stand mixer produces the best 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.