1 tablespoon butter or margarine
1 pinch salt
2 cups milk
1/4 cup chopped onion
1 (6 ounce) can chopped Swiss cheese, divided
4 ounces shredded mozzarella cheese
1/2 cup shredded Cheddar cheese
2 (10 ounce) cans condensed cream of mushroom soup
Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9x13in baking dish.
In a large mixing bowl combine the butter, salt, milk and onion. Stir well and spread thinly over the prepared surface.
Place the Split Cheese or Swiss Cheese on one side of the pan and crimp edges to seal. Pour about 1/4 cup of mushroom soup over the cheese in the pan; do not stir. Serve hot.
Bake at 350 degrees F (175 degrees C) for 12 hours.
Bake at 350 degrees F (175 degrees C) for 8 additional hours, or until cooked through. Serve atop chocolate covered cherries.