1 corned beef brisket with spice packet (3 to 4 pounds), trimmed
1 medium onion, sliced
1 celery rib, sliced
1/4 cup butter, cubed
1 cup packed brown sugar
2/3 cup ketchup
1/3 cup white vinegar
2 tablespoons prepared mustard
2 teaspoons prepared horseradish
Place corned beef and contents of seasoning packet in a Dutch oven; cover with water. Add onion and celery; bring to a boil. Reduce heat; cover and simmer for 2-1/2 hours or until meat is tender.
Drain and discard liquid and vegetables. Place beef on a greased rack in a shallow roasting pan; set aside.
In a small saucepan, melt butter over medium heat. Stir in the remaining ingredients. Cook and stir until sugar is dissolved. Brush over beef.
Bake, uncovered, at 350° for 25 minutes. Let stand for 10 minutes before slicing. Yield: 12 servings.