Step 1: Cut the pork belly into large chunks. Put them in a pot with cold water, scallions, ginger, and Shaoxing wine. Bring to a boil, skim off the foam, and cook for 3 minutes. Rinse with warm water and set aside.

Step 2: Heat a wok, add oil and a few pieces of rock sugar. Cook over low heat for about 2 minutes until amber. Add the pork and toss to coat. Add dark soy sauce and light soy sauce. Stir well. Pour in boiling water to cover the meat. Add bay leaves, cinnamon stick, and bai zhi.

Step 3: Bring to a boil, then turn down to low heat. Simmer for 1.5 to 2 hours until tender. Add salt to taste near the end.

Step 4: In a bowl, mix flour, yeast, sugar, and warm water. Stir and knead until smooth. Cover and rest for 10 minutes.

Step 5: Roll the dough into a log, cut into 12 pieces. Roll each into a ball, then flatten into an ox-tongue shape. Fold, roll up, seal, and press flat. Roll into a thick disc.

Step 6: Cover the shaped buns with plastic wrap and rest for 30 minutes.

Step 7: Heat an electric griddle or non-stick pan over medium heat (no oil). Cook the buns covered until both sides are golden brown and puffed. Press with a spatula; if they spring back, they are done.

Step 8: Let the braised pork cool, then chop finely. Mix with scallions if desired. Slice the bun open, stuff generously with the pork, and serve.