Slice pork belly into 2-inch wide strips. Bring a large pot of water to a boil, and stir in pork slices; reduce heat to a simmer, and cook the meat for 10 minutes. Remove from the water and blot dry with paper towels.

Heat vegetable oil over medium-high heat in a large wok. Brown pork strips well on all sides. Pork will splatter — use a splatter shield for this step.

While pork is browning, mix together light soy sauce, dark soy sauce, rice wine, rock sugar, ginger, and spring onions in a large soup pot or stockpot. Bring the mixture to a boil, stirring to dissolve sugar. Reduce heat to a gentle simmer and lay the pork strips into the liquid. Cover, and simmer until the meat is very tender, 1 1/2 to 2 hours. Add water as needed to keep the liquid from going completely dry.