In a large bowl, combine bread cubes, onion, parsley, sage and the egg. Add enough broth until stuffing is moistened and holds together. Stuff loosely into chicken. Fasten with skewers to close. Place with breast side up on a shallow rack in roasting pan. Brush with butter if desired. Bake, uncovered, at 375° for 1-3/4 to 2-1/4 hours or until juices run clear. Baste several times with pan juices or butter. Prepare gravy if desired.