Trim the stems of shiitake mushrooms, slice the caps thinly, and cut the stems into thin strips. Thinly slice the onion.

Rub the pork belly slices with a pinch of salt and pepper.

Heat salad oil in a frying pan over medium heat. Add the pork and cook until the color changes. Push the pork to the side, add onion and shiitake mushrooms, and stir-fry until the onion becomes tender.