Add onions, 2 unpeeled carrots, celery, garlic, and pickling spice and simmer 2-1/2 to 3 hours or until very tender.
Remove corned beef, let rest.
Remove all vegetables from cooking liquid and discard. Add potatoes, peeled carrots, and cabbage wedges and simmer 20 to 30 minutes or until tender.
Slice corned beef, against the grain, into thin slices. Serve with vegetables, grainy mustard, rye bread, and Guinness!
Keto friendly without the carrots and potatoes.