I used swiss cheese but you can use what cheese you like.
1 lb. lean ground beef
8 slices each: bread
4 slices each: swiss cheese
1/8 - 1/4 c. butter
Non stick cooking spray
1 onion sliced
1/8 - 1/4 tsp. each: salt, pepper
1 T. oil
Remove meat from refrigerator and shape meat into patties.
Sprinkle salt and pepper on both sides of hamburger, set aside for a few minutes.
Remove stick of butter from refrigerator and let it set out for a few minutes to soften.
Remove cheese from refrigerator.
Peel, rinse, slice onions, set aside on a plate.
Preheat grill pan to medium to high heat.
Lower heat to medium and spray pan with nonstick cooking spray.
Add hamburger patties and cook on 1 side for 5 - 8 min.
Turn hamburger over and cook on other side for 5 - 8 min. more.
Remove patties from pan, lower heat and add oil.
Add onions, grill onions for a few minutes.
While hamburgers, onions are cooking, toast bread slices.
Remove bread from toasters and butter both sides of bread, set aside.
Place the buttered side up of 4 slices of bread on a clean work area or cutting board.
When onions are done, remove onions.
Place bread slices in pan, top bread with burgers.
Layer cheese, onions on the burger and grill on 1 side for a few minutes or until cheese is melted.
Top burgers with with remaining bread slices.
Flip over and cook on other side for 3 - 5 min more or until brown.
Makes 4 servings.