Slice the pork belly into 2-inch wide strips. Bring a large pot of water to a boil, and stir in the 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 the vegetable oil over medium-high heat in a large wok, and brown the pork strips well on all sides. Pork will splatter - use a splatter shield for this step.
While pork is browning, mix together the 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 the 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.
