Place celery and onions in slow cooker; top with corned beef brisket. Sprinkle contents of seasoning packet over brisket. Add 2 cups water and cola. Cover; 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.
Recipe courtesy of The Beef Checkoff.