1 can cream of chicken soup
1 cup milk
1/2 cup chopped onion
1 cup sour cream
1 cup grated cheddar cheese
4 cups frozen hash browns (may be thawed, it doesn't matter)
For the topping:
2 cups crushed cornflakes
1/4 cup melted margarine
1/4 cup Parmesan cheese
Mix soup, milk, onion, sour cream and grated cheddar cheese in bowl.
Mix well and add hash browns.
Mix well and put in greased casserole dish.
Mix cornflakes, margarine and Parmesan cheese and pour over potato mixture.
Bake uncovered at 350°F for one hour.