Remove and discard tough outer leaves from cabbage. Shred cabbage very fine. In heavy kettle, melt butter. Add sugar, but do not brown. Add cabbage and cook 3 minutes, stirring constantly. Add vinegar, water, salt and pepper to taste. Simmer covered for 2-3 hours, or until cabbage is very tender. Stir occasionally, and if necessary, add a little hot water to prevent scorching. When cabbage is almost tender, add apples, if desired, and red currant jelly. Cabbage should be quite sweet-sour. If necessary, add more sugar or vinegar, a little at a time. Simmer covered for 30 minutes longer, stirring occasionally. Serve with roast goose or duck. This is best if made a day ahead, and reheated slowly.
Serves 4.