Bring a pot of water to boil and place pork belly inside, along with ginger, garlic and scallion; let cook for 30 minutes until meat is firm.
Heat oil until hot; stir fry ginger, garlic, scallions, star anise and cinnamon until fragrant, about a minute. Add soy sauces, rice wine, brown sugar and water. Bring to a boil, then turn off heat and stir until sugar is melted. Pour on top of and in between pork belly slices. Place piece of parchment paper on top to cover the pork belly.
Chinese pickled sour mustard greens are also a nice accompaniment to pork belly buns. To prepare this, soak pickled sour mustard greens in water for 1/2 hour. Drain and mince. Saute with a little sugar and salt.