Partially freeze beef; slice thinly across the grain into bite-size strips. Chop the bok choy; set aside. Cut the carrot and green bell pepper into matchstick size pieces; set aside. Bias slice the celery into 1/2 inch lengths; set aside. Thinly slice the green onions; set aside.

In a small bowl stir together the dry sherry, soy sauce and the chili oil. Crush the Szechuan peppercorns and add to the soy sauce mixture; set aside.

Preheat a wok or large skillet over high heat; add cooking oil. Stir fry onions for 1 1/2 minutes. Add bok choy and celery; stir fry 1 minute more. Add carrot and green bell pepper; stir fry 2 minutes more. Remove vegetables. Add more oil if necessary. Add half of the beef to the wok. Stir fry 2-3 minutes. Remove beef. Stir fry remaining beef 2-3 minutes. Return all meat to wok.

Stir soy sauce mixture; stir into wok. Cook and stir for 1 minute or until heated through. Stir in vegetables; cover and cook 1 minute. Serve over steamed or fried rice.