Soft, fluffy steamed buns filled with a molten lava-like salted egg yolk custard. These custard buns aka liu sha bao 流沙包 are a cute, must-have dim sum!
If there’s one thing that always reminds me of slow weekend mornings at yum cha with my family, it’s soft steamed custard buns. There’s something comforting about that warm, fluffy dough and the smooth, salty-sweet centre that melts the moment you tear it open. The filling has a rich, sandy texture that turns creamy as it warms, and it feels simple but a bit special at the same time.
I first started playing with salted egg custard back when I was testing recipes for TuCha, trying to get that balance of sweet and savoury just right. A few batches were too firm, a few burst open, and one even glued itself to the steamer because I forgot the paper squares. But when it finally came together, it tasted like the versions I grew up with, only a touch richer. This is the version I go back to when I want something soft, warm, and a little nostalgic.
What are steamed custard buns?
Steamed custard buns are a classic Chinese treat. Originating in Southern China these custard buns are a popular dim sum and a staple at any yum cha feast.
Typically eaten for breakfast, or as a snack, these are made with a creamy custard and soft fluffy steamed bun. How can you go wrong with a custard-filled bun right?
When it comes to custard buns there are two distinct types. Both are called custard bun, but one is filled with a thick and creamy egg custard and the other is filled with a molten salted egg custard. The first is called nai wong bao 奶黄包, while the other is called liu sha bao 流沙包. Both absolutely delicious but distinctly different.
Nai wong bao 奶黄包
Nai wong bao literally translates to “milk egg yolk bun”, and is made from regular chicken eggs and milk to form a custard. The custard is then chilled and rolled into balls before being filled in the bao dough. The custard is usually thick and creamy, reminiscent of western custards like creme patissiere.
Liu sha bao 流沙包
Liu sha bao literally translates to “flowing sand bun”. These are made from salted duck egg yolks, butter, and custard powder to form a sweet and savoury custard that is runny and slightly grainy when steamed.
The buns we are making today are the latter, and my personal favourite of the two. The salted egg yolk adds a salty and savoury touch to an otherwise sweet bun, making them even more delicious.
And of course, there is so much more drama with a molten lava-like centre. If you can’t find salted egg yolks, or aren’t fond of them, feel free to substitute the salted egg yolks with regular egg yolks.
At-a-Glance – What You’ll Need Before We Start Rolling
| Yield | Prep Time | Cook Time | Difficulty | Storage |
|---|---|---|---|---|
| 12 buns | 30 minutes | 15 minutes | Intermediate | 3–4 days refrigerated or freeze before steaming |
Main Ingredients
Here are the essentials you need to make soft bao and a molten salted egg custard.
- Cake Flour: Cake flour keeps the dough soft and light, just like the bao you get at dim sum.
- Whole Milk: Warm the milk a little so the yeast wakes up faster and the dough rises evenly.
- Instant Yeast: Make sure it’s fresh. Old yeast makes buns dense and slow to lift.
- Unsalted Butter (for the custard): Soft butter blends smoother and gives the filling that creamy molten finish.
- Cooked Egg Yolks (salted or regular): Mash them very fine so the custard stays silky once steamed.
Optional – My Favourite Extras That Add a Little Magic
These aren’t required, but they add fun flavour or colour when you want to play around.
- Yellow Food Colouring: Adds that warm golden look that makes the buns extra cute.
- Milk Powder: Deepens the custard flavour and makes it taste richer.
- Custard Powder: Helps the filling set and gives that classic sweet custard smell.
Substitutions – Smart Ingredient Swaps That Still Taste Amazing
If you don’t have everything on hand, these swaps still give you beautiful bao.
- Cake Flour → All-Purpose Flour + Cornstarch
Swap Tip: This lightens the dough and keeps the bao soft enough for steaming. - Salted Duck Yolks → Regular Egg Yolks + Salted Butter
Swap Tip: The flavour is milder, but the custard will still be smooth and rich. - Whole Milk → Oat or Soy Milk
Swap Tip: Use lukewarm milk so the yeast still rises well.
How to create the molten salted egg filling
The highlight of these buns is the molten, lava-like filling that runs out of the buns (or the mouth of these cute buns!) Here are a couple of tips to help you achieve a delicious, runny bun.
Mash the salted egg yolks
If you’ve had a salted egg yolk bun before you will know that the filling is a little grainy. This graininess comes from the salted egg yolk as we are mashing steamed egg yolks rather than whisking raw egg yolks into a custard. To get the perfect texture make sure you mash your egg yolks into a fine sand-like texture before mixing with the rest of your ingredients
Chill the filling
Once you have combined all the ingredients together it will be quite loose and wet. This is completely normal! As the filling is made predominantly of butter it is important to chill it. That way we will be able to roll it into balls. Place the filling in the fridge, and once it has chilled and firmed up, divide it into 12 equal portions.
Don’t oversteam your buns
Once you have filled your buns with the salted egg yolk balls it’s time to steam them! One of the most important things to keep in mind when making these is the steam time and temperature.
If you steam these on high heat the buns will get bubbly and the egg yolk custard will disappear into the buns.
If you steam these for too long, the custard will also dissolve into the buns.
Make sure you steam these buns over medium heat for 8-9 minutes. Then leave the buns in the steamer for 5 minutes so they can set. This is the perfect timing and heat for a liquidy filling that doesn’t get soaked up by the fluffy dough.
Troubleshooting – Quick Fixes I’ve Learned from My Bakery Kitchen
| Issue | What’s Happening | Quick Fix |
|---|---|---|
| Custard leaks while steaming | Pleats not sealed tight | Pinch seams firmly and chill buns before steaming |
| Buns come out wrinkly | Dough overproofed or steam too high | Proof shorter and keep steam at medium heat |
| Filling disappears | Steamed too long or too hot | Steam 8–9 minutes only and rest in the steamer |
| Buns turn dense | Dough under-kneaded | Knead until smooth and elastic |
| Custard too firm | Not enough butter or yolks mashed too coarse | Mash yolks finer and add a touch more butter |
Comparison – How This Recipe Stacks Up Against Other Desserts
| Dessert | What Makes It Different | When I Reach For It |
|---|---|---|
| Egg Custard Buns | Soft bao with a molten salted egg centre | When I want something warm, nostalgic, and a bit playful |
| Nai Wong Bao | Smooth, creamy milk-based custard | When I’m craving something sweeter and less salty |
| Charcoal Custard Bao | Dramatic dark dough with golden filling | When I want a fun colour contrast for parties |
Tips for Perfect Salted Egg Custard Buns
Choose the right flour for softness
If you can source Hong Kong flour or a low-protein flour blend, you’ll notice a lighter, fluffier bun. This flour yields a pillowy texture that melts on the tongue.
Love that melt-in-mouth softness? Try my Red Bean Buns – sweet, tender, and filled with earthy bean goodness.
Use a pinch of baking powder
Alongside yeast, a small amount of baking powder gives the dough an extra boost. Think of it as a gentle lift, ensuring buns puff beautifully.
Firm the custard overnight
Chilling the filling until completely solid, even overnight, makes wrapping so much easier. Firm custard holds its shape, reducing leaks during steaming.
Pleat with precision
A neat pleat is more than pretty. Gentle pleating helps evenly seal the filling and prevents molten custard from escaping mid-steam.
Adjust steaming from frozen
If you freeze unsteamed buns, steam them directly from frozen with an extra two to three minutes. This keeps the filling molten without overcooking the dough.
Substitute custard powder wisely
If custard powder isn’t available, combine cornstarch with a little vanilla or milk powder. This creates a similar creamy texture and subtle sweetness.
Craving something classic? My Cream Buns are rich, fluffy, and filled with old-school bakery charm.
Variations to Try
Charcoal custard buns
Mix a touch of food-grade charcoal powder into the dough for dramatic black buns. The contrast against golden custard is striking and makes for a memorable dessert.
Matcha lava bao
Add matcha powder to the custard for an earthy bitterness that balances the sweetness. The green lava oozing from the bun is both unique and eye-catching.
Chocolate salted egg buns
Incorporate cocoa powder or melted dark chocolate into the custard. The result is a molten blend of rich chocolate and savory salted egg.
Deep-fried golden buns
After steaming, shallow fry the buns until crisp on the outside. The crunch gives way to a molten center, offering a delightful texture contrast.
Evaporated milk custard
Replace milk with evaporated milk in the filling. This small change gives the custard a richer, almost caramel-like flavor with extra creaminess.
Mini custard buns
Shape smaller buns perfect for parties or afternoon tea. These one-bite molten treasures are easier to serve and create less mess when sharing.
Serving Suggestions
Pair with floral teas
Serve with jasmine, chrysanthemum, or oolong tea. Their delicate notes cleanse the palate, cutting through the richness of the custard.
Present in bamboo steamers
Arrange buns in traditional bamboo steamers for an authentic yum cha presentation. Guests love the reveal of steam when the lid is lifted.
Create a brunch centerpiece
Combine with tropical fruits like mango, lychee, or dragonfruit. The fresh, bright flavors balance the indulgent buns for a beautiful brunch spread.
Dessert tower display
Stack buns on a tiered stand for a playful take on a dessert tower. This presentation feels celebratory and is perfect for festive occasions.
Drizzle with condensed milk
Lightly drizzle buns with condensed milk before serving for an extra touch of sweetness and glossy finish.
Shape for children
Make playful versions shaped like bears or bunnies. When broken open, the golden custard adds a surprise that children find irresistible.
Common Mistakes to Avoid
Skipping the mash
Leaving salted yolks too chunky leads to unpleasant lumps. Mash yolks finely into a sand-like texture for a smooth yet slightly grainy custard.
Loose pleating
If buns are sealed loosely, custard will leak during steaming. Pleat carefully and pinch firmly to ensure a neat closure.
Custard too warm
Filling that isn’t chilled will ooze out during wrapping. Ensure the custard is firm enough to roll into balls before use.
Overproofing the dough
Proofing too long weakens the gluten structure. Overproofed buns often collapse or wrinkle after steaming.
Thick dough edges
If the wrapper is too thick at the top where pleats gather, the bun may steam unevenly. Roll dough evenly, leaving edges slightly thinner.
Using the wrong steaming setup
Steamers with excessive condensation can drip onto buns and make them soggy. Place a cloth under the lid to catch water droplets.
Frequently Asked Questions
Why Are My Buns Wrinkly?
There are a couple of reasons why your buns may have wrinkled:
- There Were Too Many Air Bubbles In The Dough: If you don’t knead your dough enough after the resting time there will be air bubbles that appear on the surface after the buns have steamed.
- The Dough Was Overproofed: if you let your dough proof for too long they will expand beyond the size they are able to support. As a result, when steamed they will continue to expand, before shrinking as they come away from the heat.
- The Buns Didn’t Get To Rest: If you don’t allow your buns to rest after steaming they will deflate. Make sure you leave the buns in the steamer for 5 mins before opening the lid to prevent them from deflating.
- The Heat Was Too High When Steaming: if the heat is too high the buns will expand rapidly before shrinking and becoming wrinkly.
Why Aren’t My Buns Fluffy?
A few reasons:
- The Dough Wasn’t Kneaded Enough: The dough needs to be kneaded in order to form gluten networks. These help support the air that forms in the buns as they proof and steam. Without these networks, you’ll have dense buns
- The Buns Were Underproofed: If you don’t give your buns enough time to proof before steaming they won’t be able to expand to their full potential. As a result, they will be a lot denser.
How Come My Buns Collapsed?
A few reasons:
- The Dough Was Overproofed: If the buns were overproofed they will have too much air that is unsupported. This will result in the collapsing right out of the steamer.
- The Buns Didn’t Get Time To Rest: If you open the steamer right after the buns have finished steaming the sudden change in temperature will cause them to deflate.
Where Did My Custard Go?
The most important thing about custard buns is the timing.
If you steam these for too long, or on too high of a heat the custard will slowly disappear into the bun. Make sure you steam the buns over medium heat and keep a close eye on the timer, they should not steam for more than 10 minutes.
How Do I Store These?
Once steamed you can store these in an airtight container in your fridge for 3-4 days. When ready to eat, steam them for 5 minutes to return them to their original fluffy texture.
You can also place them in a bowl with a splash of water. Cover the bowl with a plate, and microwave for 1-2 minutes. However, I find the texture is never as fluffy as when they are steamed!
Can I Freeze These?
Yes definitely! I usually make a large batch of these and freeze them.
Whenever I’m looking for a quick and easy breakfast or snack I can then take them out and steam them from frozen. These should take about 10 minutes to reheat when steaming from frozen.
Can I make these without salted duck eggs
Yes, you can substitute chicken egg yolks and add salted butter for a similar savory flavor. The result will be less intense but still delicious.
Why does the filling taste grainy
The slight graininess is natural from mashed salted egg yolks. To avoid unpleasant lumps, mash yolks finely before combining with other ingredients.
Can these be baked instead of steamed
Yes, though the texture changes. Baking produces bread-like buns rather than fluffy steamed bao. The custard will still melt, but the crust is firmer.
Are these safe for children
Yes, they are suitable for children as long as the filling is fully cooked and the buns are cooled slightly before serving.
How can I stop custard from leaking
Chill the filling until solid, then seal the buns with neat pleats. Avoid over-steaming, as too much heat causes custard to dissolve into the dough.
What teas pair best with these buns
Jasmine, oolong, and chrysanthemum teas are excellent choices. Their floral and slightly bitter notes cut through the rich, sweet custard.
Let’s Get Cooking
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Egg Custard Buns
Sofft, fluffy steamed buns filled with a molten lava-like salted egg yolk custard, these custard buns aka liu sha bao 流沙包 are a cute, must-have dim sum!
- Prep Time: 30 minutes
- Cook Time: 15 minutes
- Total Time: 45 minutes
- Yield: 12 Buns 1x
- Category: Bread
- Method: Intermediate
- Cuisine: Chinese
Ingredients
Bao Dough
- 300g Cake flour (3 cups)
- 180g Whole milk (3/4 cup), lukewarm
- 1 tbsp White sugar
- 1 tsp Instant yeast
- 1 tsp Vegetable oil
- Yellow food colouring, optional
Egg Custard
- 2 Cooked egg yolks (salted duck or regular)
- 60g Unsalted butter (1/4 cup), room temperature
- 50g Icing sugar (1/2 cup)
- 20g Milk powder (2.5 tbsp)
- 20g Custard powder (2.5 tbsp)
Instructions
Egg Custard
- Mash the egg yolks until smooth with a fork
- Combine the butter and sugar in a bowl and whisk until smooth
- Add the mashed yolks, milk powder and custard powder, and mix until smooth
- Divide into 12 balls and refrigerate until firm
Bao dough
- Cut 12 pieces of baking paper at 5 x 5cm / 2 x 2 inches
- Combine the flour, lukewarm milk, sugar and yeast, in a large bowl and mix until just combined
- Then knead until a rough ball,
- Remove a small handful of dough for the eyes, if making and colour the rest of the dough with yellow food colouring (If you want to make them yellow with eyes, otherwise proceed to divide the dough into 12 balls without colouring)
- Divide into 12 balls and cover
- Allow the portioned balls to rest for 10 minutes
- Uncover and knead each ball until smooth, then flatten and fill with a ball of custard
- Seal and place on a square of baking paper
- Place on a baking tray or in a steamer and cover
- Proof for 45 mins or until the buns have grown, but not yet doubled in size
- Bring a large pot of water to a boil and reduce the heat to medium-high
- Place the steamer over the pot of water and steam the buns for 8-9 mins
- Allow the buns to rest in the steamer after cooking for 5 mins then enjoy
I could not get this dough to come together at all. It was so dry and crumbly. Is that the correct texture?