Rinse corned beef under cold water.
Place in large pot with water/beer, spice packet, onion, garlic.
Boil then simmer covered 3 hours (fork-tender, 195°F).
Add carrots + potatoes last 30 min.
Quarter cabbage (remove core), slice 2" wedges.
Add cabbage final 15-20 min until tender-crisp.
Rest beef 10 min, slice against grain.
Serve with mustard, horseradish, Irish soda bread.