1. Preheat over to 325°F. 2. Wash corned beef brisket. Place in large roasting pan on oven rack. Cover meat with boiling water; add pickling spices; cover pan with aluminum foil. 3. Bake in preheated oven for 2 hr. or until tender when pierced with two tined fork. Allow to cool in cooking liquid. (This can be done the day before; refrigerate) 4. Prepare Horseradish Sauce; refrigerate. 5. About 1 hr. before serving, drain cooked corned beef and place in roasting pan. 6. Bake at 325°F for 30 min. 7. Combine brown sugar and mustard in small bowl and spread over corned beef. Bake 30 min. longer or until well glazed. 8. Cut into thin slices and serve with Horseradish Sauce. Garnish with wedges of orange and sprigs of watercress.