Place sliced onions in Crock-Pot; pour in butter and mix to coat onions thoroug hly. Stir in cubed bread. Add chicken broth to cover; stir well. Cover and c ool on Low for 10 to 18 hours or on High for 4 to 5 hours, stirring occasionall y. Stir well during last hour. Serves 6 to 8