Heat the oil in a wok over low heat. Add the pork belly and cook just until the fat is translucent (don’t cook it for too long, or it will become tough). Add the red bell pepper and turn the heat up to medium.
After stir-frying for about 30 seconds, turn the heat all the way up to high and toss in the leeks, along with the Shaoxing wine, white pepper, sesame oil, sugar and light soy sauce. Continue to stir-fry until the leeks are wilted. Serve!