Put the sliced steak into the glass bowl and sprinkle the sugar on top. In the small bowl, stir together the soy sauce, sherry, cornstarch, and oil and then pour over the steak. Toss until the steak is coated, and set aside for about 30 minutes.
While the steak is marinading, prepare the remaining ingredients. Make sure everything is chopped, minced, and measured, because the process moves pretty quickly once you begin stir frying.
Heat the wok over high heat. If you have a gas range or cooktop, use the highest output burner. Add 2 tablespoons of the oil to the wok, and it should move quickly around the wok if the temperature is correct. Add the meat, stir frying for about 3 minutes, until the meat is cooked about 75% through. Remove the meat to the other medium bowl (do not put back into the marinade bowl).
Add 2 more tablespoons oil to the hot wok and add the bell peppers, stirring for about 2 minutes. Add the scallions and the black bean sauce, stirring for about 2 minutes. Add the garlic and ginger, stirring for just a minute.
Return the meat and all it's juices back to the wok, stirring for 1 minute until it's heated through. Add the chicken/vegetable stock and cook until it starts to boil.