Make the dough: In a bowl, mix yeast, plain flour, white sugar, and warm water. Mix everything into a dough and knead until smooth. Cover it with plastic wrap and let it rest for 20 minutes. Do not skip the resting step. Resting is key to letting the gluten relax and hydrate, making it better able to hold its shape. Moreover, it gives the yeast time to ferment and let the dough rise.

Blanch the pork belly: Meanwhile, cut the pork belly into small pieces and blanch them to remove any impurities. Begin the cooking process by immersing them in cold water. Blanch for 3 minutes and scoop out any scum floating. Then, remove them from the pot and drain well.

Stir-fry the pork belly: Then, heat oil in a pan and add rock sugar. Stir-fry until it caramelizes. Next, add the pork belly and stir-fry until brown and glazed.

Stew the pork belly: Add dark soy sauce, chopped green onions, ginger slices, Sichuan peppercorns, star anise, bay leaf, and cinnamon. Pour in water until the pork belly is submerged.

Simmer: Simmer for 20 minutes, then add cooked eggs, salt, chicken bouillon powder, and MSG if you're using it. Cover and stew over low heat for 30 minutes. I suggest cooking the pork belly ahead of time and letting it sit in the stew overnight to fully absorb the flavors.

Knead and shape the dough: While simmering, knead the dough once more to remove air bubbles. Divide it into 8 portions and shape each into a round ball. Take one portion and roll it out into a thin oblong sheet. Fold it in half, then roll it up starting from one end. Once rolled into a spiral, flatten it with your hand and roll it with a rolling pin. This should give you flat discs.

Cook the bun: Heat a non-stick pan and cook the bun until both sides have golden brown marks.

Make the filling: Take out the pork belly and eggs from the stew and finely chop them with green peppers and coriander.

Assemble: Slice the bun in half without completely cutting through. Stuff it with the juicy filling, and serve it with a spoonful of juicy soup made from the stew.