Cut the pork belly into ¼" thick pieces that will fit approximately 2 pieces to each bun.
Bring a pot of water to a boil. Add the pork and cook for 3-4 minutes, then strain, rinse, and discard water.
Place a wok or large skillet over low heat. Add the oil and sugar and cook until sugar has melted.
Raise the heat to medium and add the pork. Cook for 2-3 minutes, stirring frequently, until pork is just starting to brown and crisp at the edges.
Add the shaoxing wine, light and dark soy sauce, and water. Cover and simmer for 45 minutes, or until pork is fork tender. Stir frequently to avoid burning the sugar, adding more water if the pan gets too dry.
Once the pork is tender, remove the lid and simmer uncovered until the liquid has formed a thick, syrupy sauce that sticks to the pork belly.
Serve over rice, in steam buns, etc.
NOTE: It is very important to the flavor and color of the sauce that both soy sauces are used.