Let your slow cooker do all the work for this complete meal of beer-braised Corned Beef with fresh cabbage and red potatoes. It's a great dish for your next celebration.
Place celery and onions in 4-1/2- to 5-1/2-quart slow cooker; top with corned beef brisket. Sprinkle contents of seasoning packet over brisket. Add 2 cups water and beer. Cover and cook on HIGH 6 to 7 hours or on LOW 9 to 10 hours or until brisket is fork-tender. (No stirring is necessary during cooking.)
Meanwhile, place cabbage, potatoes and carrots in 2-1/2 quart microwave-safe dish; add remaining 1/2 cup water. Cover; microwave on HIGH 15 to 18 minutes or until vegetables are tender, stirring or rearranging once. Drain; remove and discard cores from cabbage wedges. Add butter; season with salt and pepper, as desired. Toss to coat; keep warm.
Prepare Red Currant-Mustard Sauce. Place jelly in medium microwave-safe bowl. Cover; microwave on HIGH 1-1/2 to 2 minutes or until melted, stirring once. Whisk in mustard. Cover; microwave on HIGH 30 seconds. Stir; keep warm.
Remove brisket and carve diagonally across the grain into thin slices. Serve with vegetables and sauce. Garnish with parsley, if desired.