Sift cornstarch, baking powder, and flour together, then add to your stand mixer with the dough hook attachment. Add sugar and instant active yeast and turn the mixer onto stir.
Turn the stand mixer on low and slowly add the water and vegetable oil. Continue to mix the mixture for about eight minutes until the dough is released from the sides and is smooth.
Remove, take off from the bowl, shape the dough into a ball.
Lightly grease the inside of the mixing bowl with one teaspoon of neutral oil and place the dough back into the bowl. Cover with a damp towel and leave it to proof for at least two hours near a warm windowsill.
Chop your char siu into small pieces about three millimeters.
In a saucepan, add the oyster sauce, light soy sauce, dark soy sauce, sugar, five spice, garlic, and sesame oil and mix thoroughly. Cook this on medium-high heat.
Mix the cornstarch and water in a separate bowl and add into the saucepan. When the mixture reaches a boil, lower to medium heat and continue to cook for another two minutes or until the consistency is similar to molasses.
Add the char siu pieces to the pan and cook for an additional minute.
Remove the char siu filling from the heat and allow it to rest on the counter.
Assembly and steaming
After two hours of proofing, your dough should have doubled in size. Move the dough onto a floured surface and lightly knead the dough with the heel of your hand for about one minute until it’s smooth and shape into a ball.
Weigh the dough and divide that weight by 16, for our dough, we averaged about 60-62 grams per piece. Shape the dough into a log and use a knife to cut pieces of dough and then weigh them to make sure all the pieces are about the same weight.
Take one piece and use a rolling pin to roll it out into a three inch diameter circle. If necessarily, sprinkle flour on the surface to prevent sticking. Then, use your rolling pin to thin out the edges of the circle while keeping the middle section the same thickness. Your dough should be the size of about 3 ½ to 4 inches now.
Add two tablespoons of char siu filling in the middle of the circle.
To fold, hold your wrapper filled with meat on your non-dominant hand. With your dominant hand, take your thumb and pointer finger and begin to fold the edges around the meat. This should look like pleating. I like to use my non-dominant hand’s pointer and index finger to guide more dough into the pleating. Continue to pleat in a circle until you reach the first pleat and close off the entire top with a pinch. The bao should have a swirl pattern on the top. Repeat with the rest of the baos.
Before steaming, cover the wrapped bao with the same damp cloth from before and proof again for about ten to 15 minutes.
Line your steamer with parchment paper or lettuce.
Add about one and a half inches of water in your pot, but not too much that it’s touching your steamer. Preheat your steamer before adding the bao for about two minutes.
Add your bao into the steamer and leave space between each bao.
Steam the bao for about ten minutes and do not remove the lid during this time.
After they’re finished, remove the bao from the steamer and serve immediately.
You can freeze the cooked bao once it has cooled, in an airtight container. To reheat frozen bao, wet a paper towel and cover the bao. Microwave the bao in 30 second intervals until the bao is fluffy and hot.