Preheat oven to 350 F. Lightly grease a 9x13 baking dish; set aside. In an extra large bowl, combine soup, onion, sour cream, cheddar cheese, milk, salt and pepper. Stir in potatoes. Spread mixture evenly in prepared baking dish. Cover and bake for 45 minutes; stir potatoes. Sprinkle with corn flakes. Bake, uncovered, for 20-25 minutes more or until heated through and bubbly. Let stand for 10 minutes before serving.