Combine the pork, scallions, garlic, and ginger in a bowl.
Add the soy sauce, shaoxing wine, sesame oil, sugar, salt, pepper, and cornstarch. Mix until it all just comes together.
Take the gelatinized broth and cut into small cubes. Carefully mix with the ground pork. Set aside or in the refrigerator until you are ready to use it. Prepare a steam basket by placing a layer of napa cabbage on the bottom, set aside.
When you are ready to make the bao, place water in a pot that can have a steamer basket placed on top of it and bring to a boil. Split the dough into 4 portions.
Take one of the portions and place the rest back under the damp towel. Cut the dough into 10 gram portions. Roll out each piece into 4 inch rounds. Add 2 teaspoons to 1 tablespoon of filling in the center. Pleat the dough until the dumpling is sealed.
Place in the prepared steamer, but do not overcrowd the steamer . Repeat this until all the dumplings are made. If there are too many, you can place them on a baking sheet and place them in the freezer. Once frozen, they can be stored in an airtight container for up to 2 months. Once the water is boiling, place the steamers on top of the pot and steam for 8 minutes (11 minutes if frozen).