Cook, remove bones, and cut chicken breasts into chunky pieces. Save 2 cups of broth to be used later. Cook spaghetti noodles until tender according to pkg. directions. For extra flavor, use remaining chicken broth in exchange for some of the water.
In a large casserole dish, place noodles layered with chicken pieces. Stir together melted butter, soup, sour cream, and chicken broth with salt and pepper. Pour this mixture over noodles and chicken.
Bake covered at 350°F for 1 hour. Remove covering and sprinkle grated cheese on top. Return to oven for 15 more minutes. Serve hot.