Brown sausage, drain and pour into large casserole. Add croutons next. Whip eggs and 2 cups milk together; pour over croutons. top with 2 cups grated cheese. Whip mushroom soup and 1/2 cup of milk together and pour over casserole. Top with hash browns and remaining grated cheese. Cover and bake at 350° for 1 hour. Uncover and bake another 1/2 hour or until cheese is bubbly and melted completely.