Brown pork in hot butter on all sides in deep kettle. Add water and all other ingredients except horseradish. Simmer, covered, for 1 1/2 hours, or until tender. Transfer meat to hot platter; keep hot. Force stock through sieve or puree in electric blender. Pour stock over meat. Top with horseradish. Serve with boiled potatoes. Makes 4 to 6 servings.