Rinse corned beef under cold water and pat dry
Place corned beef fat side up in large pot
Sprinkle spice packet over meat
Add water or broth to cover meat by 2 inches
Bring to boil over high heat
Reduce heat to low, cover, and simmer for 2.5-3 hours
Prepare vegetables while meat cooks: peel and cut potatoes, carrots, onions, and cabbage
After 2.5 hours, add potatoes, carrots, and onions to pot
Cover and cook for 15 minutes
Add cabbage wedges on top
Cover and cook another 15-20 minutes until vegetables are tender
Remove meat to cutting board and rest 10 minutes
Remove vegetables with slotted spoon to serving platter
Slice meat against the grain and serve with vegetables