In a small bowl, combine the bread crumbs, potato, onion, egg, garlic powder and 1/8 teaspoon pepper. Crumble beef over mixture and mix well. , Shape into 1-1/2-in. balls. Place in a shallow 1-qt. baking dish coated with cooking spray. In a small bowl, combine the water, soup, sour cream, mushrooms, soup mix and remaining pepper; pour over meatballs. , Bake, uncovered, at 350° for 30-40 minutes or until meat is no longer pink. Serve with noodles if desired.