Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9x13 inch baking dish.
In a large bowl, mix together the soup, sour cream, butter, dried onion flakes, and pepper. Stir in the hash browns and 1/2 the cheese. Pour into the prepared baking dish, sprinkle with remaining cheese, and top with crushed cornflakes.
Bake 45 minutes in the preheated oven, or until cheese is melted and bubbly.