4 slices process American cheese or cheddar cheese, halved diagonally
2 slices Swiss cheese, halved diagonally
4 hamburger buns, split and toasted
Lettuce leaves, sliced tomato and onion, cooked bacon strips, ketchup and mustard, optional
Combine first 5 ingredients, mixing lightly but thoroughly. Shape into 4 patties. Grill burgers, covered, on a greased rack over medium direct heat until a thermometer reads 160° and juices run clear, about 6 minutes on each side.
During the last minute of cooking, top each patty with 2 triangles American cheese and 1 triangle Swiss cheese. Serve on buns; if desired, top with lettuce, tomato, onion, bacon, ketchup or mustard.