Mix the yeast, water, and canola oil. Allow this to rest for 5 minutes or until the yeast becomes active.
Combine the flour, cornstarch, baking powder, sugar, and salt in a large bowl. Slowly mix in the liquid with the flour. Mix until it all comes together.
Transfer to a lightly floured surface and knead for 3 minutes. Place the dough in an oiled bowl and cover. Let it rest until it doubles in size, about 2 hours.
Combine all the ingredients for the filling in a bowl until just mixed. Do not overwork the filling! Split the dough into 10 equal round pieces. Place in the freezer until you are ready to form the bao.
When you are ready to make the bao, place water in a pot with a steamer basket and bring to a boil. Punch the dough and roll out into a long tube.
Split into 10 equal pieces and form into balls. Take a portion and roll out to about 6 inches wide. Avoid making it too thin. Add one of the meat balls on top.
Pleat the buns until sealed. Place on top of a small piece of parchment paper and then place in a steam basket. Make sure the bao aren’t touching. Once the water is boiling, place the steamers on top of the pot and steam for 18 minutes.