Place pigs knuckles in a large pot; add pork, onion, and water. Cook slowly, covered, for 2 1/2 hours; drain, reserve broth. Chill meat and remove fat; separate meat fron bones. Chop meat. Place meat in a kettle with 2 qts of the reserved broth. Add salt, pepper and sage; bring to a boil combine cormeal with remaining 1 qt of reserved broth and stir into boiling mixture. Cook over medium heat until thickened, stiirring constantly. Cover and cook over very low heat; stir again after 20 minutes. Pour into 2 (9-by-5-by-3-inch) loaf pans. Cool and chill overnight. Cut into slices, coat with flour and brown in butter or bacon fat. Serve hot with fruit for a hearty breakfast.