Slice beef across the grain in thin bite size pieces. Dip beef into coating mix. Place 2 tablespoons oil in wok and heat to smoking point. Quickly stir fry beef in it, no more than 3 minutes. Remove beef to a platter and reserve. Slice or shred green peppers length wise. Prepare the sauce out of the sal,t soy sauce, sugar, cornstarch and vinegar.
Heat the remaining 2 tablespoons oil to medium add the ginger, onion and sauté along with green peppers for 2 minutes. Add beef and sauce and cook for one minute. Garnish with sesame seeds Serve dish immediately.