Rinse the corned beef under cold water to remove excess salt.
Place the brisket in a large pot and cover with beef broth.
Add the quartered onion, garlic, and bay leaf to the pot.
Bring to a boil, then reduce heat and cover.
Simmer for 2.5 to 3 hours until tender.
Remove the brisket and let it rest on a cutting board.
Add chopped cabbage, carrots, and potatoes to the pot.
Cook the vegetables for about 30 minutes until tender.
Meanwhile, slice the brisket against the grain.
Serve the sliced brisket with the vegetables, drizzled with mustard.