Blend together soup, milk and pepper. Season to taste with seasoned salt and sugar. Set aside. bring 4 quarts water to boil. Add spaghetti, remove from heat and let stand til spaghetti becomes pliable, about 10 minutes.
Drain and place a layer of spaghetti in a 13 c 9 inch greased baking pan, spread with a thin layer of sour cream,sprinkle with a thick layer of cheese and top with a layer of onion. Repeat layers til ingredients are used. Pour soup mixture over spaghetti mixture. Saute crumbs in butter til golden. Sprinkle over casserole and bake at 325 for 1 hour til casserole is bubbly and spaghetti is done. Serves 10