Preheat oven to 400F
Place ground beef in large frying pan on medium heat. Add butter or margarine to taste.
When the beef is still hot, break it up.
After the ground beef is done, drain any excess grease from the saucepan.
Mix the chopped onions and ground beef in a pan. Stir until well.
Continue to cook for a few more minutes, stirring occasionally.
Turn off the heat. Once the pan is cool, add the bacon bits, mayo or ketchup mustard, salt, pepper, onion powder, and mustard. Stir well.
Spread 6 slices of bread on 1/4 cup of margarine. Then, cut them in half.
Spread the margarine side down on the bread in a greased 9x13 inch baking dish.
Sprinkle 2 cups of cheese on top.
Spread the meat mixture evenly on top of the cheese.
Sprinkle the remaining 2 cups cheese over the meat.
Spread 6 slices of bread on 1/4 cup of margarine. Cut them in half.
Spread the margarine-side down on the bread and place it on top.
Bake the dish in the oven for 20-24 minutes. 20-24 minutes.
Serve and Enjoy!