Mix the marinade ingredients and marinate the pork about 20 minutes.
Cut the tofu into 1/2-inch cubes and blanch in boiling water 2 to 3 minutes. Remove and drain.
Chop the leek or green onions into short lengths.
Heat a wok and add the oil. When hot, add the marinated pork and stir-fry until the color darkens. Add the salt and stir. Add the salted black beans and mash them with a ladle until well blended into the meat.
Add the chili bean paste, then the stock, tofu, and leek or green onions. Turn down the heat and cook 3 to 4 minutes.
While cooking, mix the cornstarch, water, and light soy sauce together. Add to the wok and stir gently. Serve with freshly ground Szechuan pepper.