Blend butter, Parmesan cheese, basil, garlic powder, 1/8 teaspoon pepper and parsley flakes with a fork until well mixed. Slit a pocket in each chicken breast half, stuff with cheese mixture and fasten with a toothpick Place chicken breasts in a 2 quart oblong casserole. Sprinkle with remaining pepper. Pour tomato sauce over chicken. Cover with wax paper. Microwave at medium high (70%) until chicken is tender, 1 6 to 1 8 minutes. Top with Mozzarella cheese slices. Microwave at medium high (70%) until cheese melts, 2 to 3 minutes. Serve over spaghetti. Makes 6 servings.