In a large bowl, combine bison, Worcestershire sauce, onion, garlic, salt, pepper, ground mustard, ketchup, chives and Italian parsley. Form into 6 patties that are slightly larger than your hamburger buns. Let sit at room temp for 30 minutes.
Grill, uncovered, over medium heat for 5-6 minutes on each side. NOTE: because of the low fat content of bison, these burgers will cook faster than beef patties. Remove from heat. Add cheese slices (optional). Place in a 250 degree F oven to melt cheese for 5 minutes.
Serve on buns or on lettuce cups for a gluten free option. Accompany burgers with lettuce, tomatoes and onion.