2 lbs. frozen shredded hash browns
2 cups sour cream
2 - 10 oz. cans mushroom soup
1/2 cup melted butter
grated onion to taste
salt to taste
2 cups grated cheddar cheese
2 Tbsp. parmesan cheese

Thaw potatoes slightly in their bag. Mix sour cream, mushroom soup, butter, onion, salt together in a bowl - warm the ingredients a bit so it mixes better. Pour hashbrowns and cheddar cheese in a 9 x 13" baking dish, mix up a bit before adding the soup/sour cream mixture. Mix well.

Sprinkle parmesan on top and bake at 350°F for 1 hour.