Cheese Potatoes

2 12 oz. pkgs. cubed hash browns (brown in butter)
1/2 cup chopped onions
1 cup grated cheese
1/4 cup butter
1 cup sour cream
1 can cream of mushroom soup

Brown onions, and hash browns in butter. Mix together sour cream, mushroom soup. Add soup mixture to browned hash browns and put in a 9 x 13 pan. Cover with grated cheese. Bake at 350 degrees for 20-30 minutes, until cheese melts, and it is warmed through.