Combine beef, onion, egg, salt and pepper, and crumbs.
Combine soy sauce, honey, sherry, ginger and garlic. Heat on low - medium in small saucepan till smooth and hot.
Let cool and add to beef mixture, mix well and shape into 8 patties. (Make a bit more sauce if it looks like it might need it ( hard to tell I know) Once I think I used too much beef and they had way too little teriyaki taste).
Grill on barbecue on med high to high heat till burgers are done (Approx 20 min? I usually eyeball them or use a meat thermometer).
Serve on buns with slices of fresh red onion, pepper and spinach.