In a small bowl, add the soy sauce, oyster sauce, hoisin sauce, sugar, corn starch, and water. Stir to combine.
Add the pork and onion to the instant pot. Cook until almost done, then add the sauce and stir to combine. Saute for 5 minutes.
Once done, remove from the instant pot and set to the side.
Clean the instant pot and dry.
In a small bowl, add the flour, instant yeast, and sugar. Stir to combine.
Add the flour mixture to a stand mixer with a dough hook attachment. Add the room temperature water to the mixture. Knead the dough mixture for 5 minutes.
Add in the salt and continue to knead until the dough is smooth.
Let the dough rest, covered, until it has doubled (about 45 mins).
Roll the dough out on a flour coated surface. Using a 4-5 inch circle cookie cutter, cut your buns out.
Work with one dough at a time. Place the filling at the center and then gather the sides to enclose the bun and pinch to seal.
Cover with a clean cloth and let them proof for about 15 minutes.
Pour 1 cup of water into the inner pot of the instant pot. Place a metal trivet in the instant pot.
You can use either a bamboo basket or a plate to steam the buns. Place it on top of the trivet.
Arrange 3-4 proofed buns in the basket or on a plate. Close the lid. Turn the steam release valve to “sealing”. Press “Steamer” and set the timer to 3 minutes. After 3 minutes of steaming, wait 1 minute and then release pressure.
Repeat with remaining bao.
Serve and enjoy!