PREPARATION:

Slow Cooker Directions

1. Coat slow cooker with nonstick cooking spray. Place onion, carrots and potatoes in bottom of 4- to 5-quart slow cooker. Drain corned beef, reserving spice packet and juices from package. Place corned beef over vegetables; pour juices over beef and top with contents of spice packet. Add enough water to barely cover beef and vegetables (about 4 cups). Cover; cook on LOW 8 to 9 hours or on HIGH 5 to 6 hours or until corned beef is fork-tender.
2. Transfer corned beef to large sheet of heavy-duty foil; wrap tightly and set aside. Add cabbage wedges to vegetables, pushing down into liquid. Increase heat to HIGH. Cover; cook on HIGH 30 to 40 minutes or until vegetables are tender.
3. Meanwhile, combine sour cream, mayonnaise, mustard and horseradish; mix well. Reserve 1/2 cup of juices in slow cooker. Drain vegetables; transfer to serving platter. Thinly slice corned beef; arrange on platter and drizzle reserved juices over all. Serve with horseradish mustard sauce.