Soft and fluffy steamed buns are filled with savory and sweet molten lava salted egg yolks custard filling that will gush out as soon as you take that first bite
Steam the egg yolks for about 5 minutes over high heat and then mash with a fork
Make sure the butter is soft but not melty or wet. Place the softened butter n a large mixing bowl, add sugar and mix until the color is pale with a whisk. Add milk, mashed egg yolk and stir in the milk powder and mix until combined. The consistency should be pasty
You can use a spoon to scoop it into a silicone ice cube tray or whatever mould you have for easier shaping. Aim for 10 pieces (depending on how small or big you want to make the steamed buns). If you don't have any tray or mould, scoop and place this on top of baking tray or a plate lined with parchment paper and put them in the freezer and let it freeze for at least 1 hour. I did mine overnight
Preparing the dough with a machine:
Place the flour (either option 1 or 2), instant yeast, salt, sugar, and cooking oil in a mixing bowl. If you are using a stand mixer, use a dough hook attachment. Gradually add liquid. If the dough still a bit dry, add a bit of water or milk. Add more teaspoon by teaspoon until the dough comes together and continue to knead for 10-12 minutes, until the dough is very stretchy and smooth
Prepare the dough by hands:
Place the flour (either option 1 or 2), instant yeast, sugar, and cooking oil in a mixing bowl. Mix everything until you get a rough dough (it's not going to be smooth yet). Cover and rest it for 15 minutes. Then go back and knead it. You'll be surprised by how easier it is to knead it now. Knead until the dough is smooth and pliable, about 15-20 minutes. Add liquid as needed. At any point during kneading, you can always stop and rest the dough if you find it hard to knead. This is to relax the gluten. Then go back to knead again and you'll be surprised by the difference it makes by just resting the dough before kneading again. It's easier for you too
Rest the dough:
Cover and rest the dough for 15 minutes. This is not to proof the dough. It shouldn't double in size. This is to relax the gluten for easier shaping and rolling the dough
Wrapping:
Place the dough on a lightly floured surface. Roll into a long log and then divide equally into 10 pieces. Work with one piece at a time and cover the rest to prevent drying. Flatten the dough with your palm and use a small rolling pin to roll into a circle about 5-6 inch in diameter and the middle is thicker. Don't roll the dough out too thin too. This is important because the filling will make the dough "wet" if it's too thin and as a result, your steamed buns will have wrinkly surfaces (wet spots)
Place the frozen filling ball in the center of the wrapper and gather all the sides to the middle and pinch to seal. Place it on a parchment paper seam side down. Make sure to seal it securely so the filling won't leak when you steam. Continue with the rest and place the bao on a large tray cover with a large clean towel
Proofing:
Let the dough rise at room temperature or at a warm place. If it's winter where you are, you can use your oven "bread proof" function to let them proof in there, or simply turn on your oven to the lowest temperature and then turn off and after 15 minutes, place the shaped buns in there to let them proof. They won't necessarily double in size, but at least puff up to about 50% of the original size. This may take about 1 hour at a warm temperature. Don't go by the time however. The buns will feel lighter and when you push on them gently with your finger, they will spring back slowly. These buns are ready to be steamed
For these steamed buns, they will tend to widen to the side a bit because the butter inside the filling has softened inside the buns during the proofing process, that's normal
Steaming:
Bring the water in a steamer to a boil. Wrap the lid with a cloth. This will prevent water dripping from the lid and create burn spots
LOWER THE HEAT TO MEDIUM. Place the buns in there, leaving about 1-inch space in between. Cover with a lid but leaving it about 1/4-inch gap for some steam to escape. Steam on medium heat for 8 minutes
Once the buns are done steaming, turn off the heat and wait for 5 minutes before opening the lid so the buns will not collapse or wrinkle due to sudden change in temperature.
Serving:
They are best when served warm. Warn whoever that is eating this that the filling is HOT and it's flowing too (like a lava!)
Storing:
Once the steamed buns have cooled down completely, place them on a baking sheet and put them in a freezer for about 1 hour. They won't be frozen yet, but firm enough. Transfer to a freezer bag and they won't stick to each other anymore. They can be kept in the freezer for up to 1 month for best result. You can thaw them overnight in the fridge and then steam them for 5 minutes to reheat or steam them from frozen for 10 minutes or until heated through
Video
Notes
You can replace salted egg yolks with same amount of mashed sweet potatoes, mashed taro, mashed ube, mashed pumpkin, etc