Preheat oven to 350º
In a medium saucepan, combine soup, sour cream, onion, & cheese.
Cook over medium to high heat until cheese is melted.
Place thawed/crumbled hash browns in a 9x13" pan. Pour melted mixture over hash browns and mix thorougly.
Fill a gallon Zip-Lock baggie with corn flakes, zip bag, and crush into crumbs.
Melt 1 stick of butter in microwave for 30-60 seconds and pour into baggie.
Mix butter into corn flakes and pour over potato mixture.
Bake at 350º for 50-60 minutes (until corn flakes begin to brown).