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!
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.
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.
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.
Let's Get Steaming!
If you're looking for a fun way to impress your family and friends, or just looking for a delicious steamed custard bun recipe this is the one for you!
If you liked this recipe make sure to leave me a comment and rating down below, I would love to know how you went.
Also, don't forget to tag me on Instagram @catherine.desserts and hashtag #cattycakes so I can see and share your desserts. Follow me on Facebook, Pinterest, Youtube, and TikTok for more of my baking creations and updates! Until next time... happy caking!Print
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
- 300g Cake flour (3 cups)
- 180g Whole milk (¾ cup), lukewarm
- 1 tbsp White sugar
- 1 tsp Instant yeast
- 1 tsp Vegetable oil
- Yellow food colouring, optional
- 2 Cooked egg yolks (salted duck or regular)
- 60g Unsalted butter (¼ cup), room temperature
- 50g Icing sugar (½ cup)
- 20g Milk powder (2.5 tbsp)
- 20g Custard powder (2.5 tbsp)
- 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
- 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
Keywords: Custard, nai wong bao, liu sha bao, buns, salted egg, egg yolk, custard, dim sum