In a skillet, cook beef and onion until meat is no longer pink and onion is tender; drain. Sprinkle with salt and 1/4 teaspoon pepper; set aside.
In a large bowl, combine pasta, 3 cups of mozzarella cheese, cottage cheese, eggs, Parmesan cheese, parsley and remaining pepper; stir gently. Pour into a greased 13x9x2-inch baking dish or shallow 3 quart baking dish.
Top with beef mixture and spaghetti sauce (dish will be VERY full).
Freeze. Cover tightly with foil. Seal additional cheese in package attached to pans.
Thaw all day in refrigerator.
Cover with new layer of foil and bake at 350ºF for 45 minutes. Sprinkle with remaining mozzarella.
Bake, uncovered, 15 minutes longer or until the cheese is melted ad bubbly. Let stand 10 minutes before serving.