Preheat oven to 350 degrees F (175 degrees C).

Place bacon in a skillet and cook over medium heat until the pieces are browned. Remove with a slotted spoon to paper towels. Discard all but 1 tablespoon of bacon grease. Stir in onions and mushrooms, and cook until soft. Remove from heat.

In a large bowl, combine beef, egg, milk, onion, mushrooms, 4 ounces of Swiss cheese, and 1 tablespoon of bacon. Mix in cornflake crumbs until well blended. Shape into a loaf and place in a meatloaf pan.

Bake in a preheated oven for 1 hour. Drain fat, top with remaining cheese and bacon, and bake until cheese is melted, about 5 minutes.