Combine beef, onion, oyster sauce, sesame seed, soy sauce and pepper; mix well. Shape into 4 patties and cook as directed below.
For Indoors: Place patties on greased rack of broiler pan. Broil both sides to desired doneness. Top each with mozzarella cheese; continue broiling until cheese is melted.
For Outdoors: Place patties on greased grill over medium coals (coals will be glowing). Grill, uncovered, 5 minutes on each side to desired doneness. Top each with mozzarella cheese; continue grilling until cheese is melted.
To serve, place each patty on bun; top with bean sprouts and pea pods.