1 (2 lb.) bag frozen hash brown chunks
1/4 c. butter
1/4 c. onion, chopped
1/2 lb. Cheddar cheese (1 c.)
1 can cream of mushroom soup
1 (8 oz.) container sour cream

Bake at 350 degrees for 1 hour, covered. Crush cornflake crumbs; mix with melted butter and sprinkle over top. Bake for 5 minutes more, uncovered.