pound of lean ground beef
tablespoons finely chopped onion
jar (2 and ½ ounces) sliced mushroom, drained
slices Swiss cheese, if desired
Mix all ingredients except mushrooms and cheese. Shape mixture into 8 patties, each about 4 inches in diameter. Top each of 4 patties with sliced mushrooms to within 1/2 inch of edges, top with remaining patty and seal edge firmly. Grill patties about on a medium grill, turning once, until desired doneness, 5 to 7 minutes on each side for medium, topping each with cheese slice durning last minute of grilling. Serve in split sesame buns if desired.