Cover drained corned beef brisket with cold water and gradually bring to a boil, skimming thoroughly. “Simmer very, very gently for about 4 hours (do not let it actually boil lest the meat be tough).” Thirty minutes before corned beef is done, drop in onions, carrots, and turnips, and cook until tender. Boil potatoes in a separate pan in plain salted water. Cook cabbage in still another pan for only 15-18 minutes. When tender, lift meat onto a large platter, and rub over with butter. Slice thinly, allowing 2 slices per serving. Garnish platter with potatoes, carrots, onions, turnips, and cabbage, and serve with fresh horseradish and mustard pickles.