Layer the potato, croutons, onion, half of the cheese, sausage, and remaining cheese in a 13x9-inch baking dish coated with no-stick cooking spray. Beat the eggs, half-and-half or milk, salt, and cayenne together and pour over the layered ingredients. Cover and refrigerate overnight. Remove the dish from the refrigerator 15 minutes before baking. Sprinkle cornflakes over the top and bake in a preheated 350 degree oven for 45 minutes or until set (may have to cover with aluminum foil last 15 to 20 minutes). Let stand 5 minutes before slicing.