Place all ingredients for the pork filling in a mixing bowl. Use a chopstick to stir in one direction until the meat is a paste-like consistency. Cover with a plastic wrap and marinate for at least 1 hour or overnight if you have the time
Once you have the basic steamed buns dough, lightly dust your work surface with a bit of flour, not too much. Flatten the dough with your palm and then use a rolling pin to roll it out to form a circle about 4-5 inches, with a slightly thicker middle part. This is to support the weight of the filling. Don't roll the dough too thin. If you roll the dough too thin, the filling might make the steamed buns "wrinkle" later when you steam
Place the filling in the middle. Create a fold around the edge and then pinch to seal. Cup the dough with both palms and move the dough in a circular motion to shape it taller. This will make your steamed buns "taller". Repeat with the rest of the dough and filling. Keep them covered with a clean tea towel
Let the shaped buns proof until about 50% double its original size. They don't have to double in size. This may take about 15-20 minutes, but please don't go by the time, just observe to make sure the buns have puffed up to half its original size before steaming. Don't overproof the buns
If your steamer is not able to steam all buns at one go, do it in 2-3 batches. Make sure to cover the rest of the proofed buns and then place them in the refrigerator to slow down the yeast activity or halt it all together until they are ready to be steamed
Bring the water in a steamer to a boil. Wrap the lid with a cloth. This will prevent water dripping from the lid creating burn spots. Place some of the buns on the steamer and steam on LOW heat for about 15 minutes. Turn off the heat and wait for 1 minute and then remove steamed buns from the steamer.
If you make extra and plan to store them, once the steamed buns have cooled down, place them on a baking sheet not touching each other and put them inside the freezer for 1 hour then transfer to a freezer bag
Chinese Steamed Pork Buns (Bak Pao) https://whattocooktoday.com/steamed-pork-scallion-buns.html