Preheat the oven to 350 degrees.
Brown one pound of ground beef and ½ of a diced onion.
Slice or dice the potatoes.
Melt three tablespoons of butter over medium heat. Add 5 tablespoons of flour to the butter once it is melted and stir. (or use a can of cream of mushroom soup)
Stir in 1 cup milk.
Spray a 9x9 or casserole dish.
Dump in the ground beef and onion mixture, one cup milk, cream of gravy mixture (or can of cream of mushroom soup), and potatoes.
Season with 1 teaspoon of salt and 1 teaspoon of pepper, and stir around.
Make sure that the potatoes are covered with the liquid.
Cover with foil and bake for 60 minutes.
Take out of the oven, remove the foil, cover with cheese, and bake for 2-5 more minutes or until the cheese is melted.