Steamed Custard Buns (Nai Wong Bao, 奶黄包)

A classic dim sum food, steamed custard buns are loved for their fluffy texture and rich flavour. Follow my recipe to make them to a restaurant standard.

A dim sum classic

If you’re a regular dim sum restaurant goer, you probably have tasted steamed custard buns (Nai Wong Bao, 奶黄包), a classic Cantonese treat made of leavened dough and an egg-milk based sweet filling. I absolutely adore its fluffy, cotton-like texture and creamy, fragrant taste.

Have you ever considered making them at home? You should definitely give it a try! My tried and tested recipe will walk you through the process with many tips and tricks to help you succeed. Here is the summary of three simple steps:

1. Follow a simple four-ingredient formula to prepare a rich, smooth filling.
2. Use the “yeast + baking powder” method to make a single-proof dough.
3. Assemble the buns then steam for 8 minutes.

Ingredients for the filling

It is said that every dim sum restaurant has its own recipe for the filling of custard buns. The ingredients required can be quite different. I’ve done extensive research and kitchen experiments to figure out the recipe I feel most happy to share.

Finally, I’ve settled for a four-ingredient formula. It’s simple, easy to make and tastes absolutely delicious. I particularly love the semi runny texture which takes the filling to the next level (It’s much softer than the custard filling used in Snow Skin Mooncakes).

For making about 8 buns, you’ll need:

• 3 yolks of hard-boiled eggs, or cooked salted duck egg yolks
• 50g unsalted butter, softened
• 30g full-fat milk powder
• 30g sugar, or 40g if using salted egg yolks

Try salted egg yolk

Both regular egg yolks and salted duck egg yolks (咸蛋黄) work for this recipe. But if available, I highly recommend you try the latter. The combination of saltiness and sweetness is a real winner with Lotus Paste and Salted Yolk Mooncake being a classic example.

Substitute for milk powder

I usually use full-fat milk powder for this recipe. However, you may replace it with custard powder (Ji Shi Fen, 吉士粉) if it’s more accessible. In this case, make sure you use traditional style custard powder which contains egg and milk. The more popular type, such as Bird’s custard powder, isn’t a great choice as it’s made of cornstarch and flavouring, etc. But it would be OK if you’d like your buns dairy-free.

Prepare the filling

No matter which type you use, the yolks need to be cooked before mixing with other ingredients. While they’re still warm, use a spoon to mash them into a fine powdery texture. If you’re a perfectionist and would like to avoid any lumps, press the yolks through a fine sieve.

Add softened butter, milk powder and sugar. Take your time to mix everything very well to create a smooth paste. Since none of the ingredients in this filling are raw, I suggest you add the sugar gradually. This way you can taste and adjust to suit your own sweetness preference.

Make the dough

The dough for custard buns is Chinese-style leavened dough that creates a soft and fluffy texture after steaming. I’ve shared a few different formulas, such as yeast only dough for Sheng Jian Bao, yeast plus baking powder version for Mantou, etc. To imitate the restaurant version, I think the formula I’ve used for Char Siu Bao and Red Bean Buns works the best for today’s recipe.

To make 8 buns, you’ll need the following:

• 175g low-gluten flour, or all-purpose flour
• 1 teaspoon instant dry yeast
• 1 teaspoon baking powder
• 1 tablespoon sugar
• 1 tablespoon neutral cooking oil
• 90g lukewarm water, adjust if necessary

Flour choices

Since steamed custard buns are a sweet treat, the best choice would be low-gluten flour which creates a soft, cotton-like texture, such as cake flour or special bao/bun flour. Buns made with bao/bun flour also look much whiter, just like what you’d get in a dim sum restaurant.

That said, please feel free to use all-purpose flour if low-gluten flour is difficult to source. In this case, slightly increase the water volume (e.g. from 90g to 95g) as flour with higher gluten content has a higher water absorption capacity.

• If making the dough manually, mix and combine all the ingredients into a rough-looking dough. Leave it to rest for 10 minutes then knead again until smooth.
• If using a stand mixer, add all the ingredients into the bowl. Run the machine at a low speed for about 8 minutes.

The finished dough should be on the soft side but not at all sticky. Since it contains baking powder, you can move on to the next step of bun assembling straightaway without proofing (unlike traditional yeast-only dough).

Roll the wrappers

Use your hands to shape the dough into a rope, then cut it into 8 equal parts. With your palm, press one piece into a disc. Flatten it into a wrapper with a rolling pin (about 9cm in diameter). Ideally, it should be slightly thinner on the edge and thicker in the middle (Please refer to the method shown in the video).

🛎 Tips: 

• To achieve a super smooth look after steaming, add one more step: knead each dough piece for about 10 seconds before you roll it into a wrapper.
• Dust the work surface and the dough with a little flour to prevent sticking. Also, make sure to cover unused dough or wrappers to avoid drying out.

Assemble the buns

Compared to Baozi (savoury stuffed buns), it’s much easier to assemble custard buns. Put a spoonful of the filling in the middle of a wrapper and seal it into a ball. No fancy pleating is required as the sealed part is facing down while steaming.

Follow the simple four-corner method shown in the image above (also in the video) or any other way you feel comfortable with. No matter which technique you use, it’s crucial that each bun is completely sealed. Otherwise, the filling will leak out when softened during steaming.

Rest and Steam

With the sealed part facing downwards, place all the buns into a steamer basket. To prevent sticking, I used cupcake paper moulds which are the perfect size for these buns. Alternatively, line the basket with parchment paper or brush a thin layer of oil if using a metal/plastic steamer.

Leave the buns to rest in a warm place to proof for about 30 minutes. During this process, they’ll grow a little bigger (but won’t double) and become plumper (the surface of the wrappers looks tighter and smoother).

Now, let’s cook! Bring water to a full boil in a wok/pot. Then place in the steamer basket. Cover with a lid. Leave to steam over medium-high heat for 8 minutes. If making a bigger batch, you can stack up 2-3 baskets and steam all at once (The cooking time remains the same).