Place the corned beef in a large Dutch oven or stockpot, fat side up. Add the contents of the spice packet, garlic cloves, onion quarters, bay leaves, and peppercorns if using.

Pour in enough cold water or beef broth to cover the meat by at least 1 inch.

Bring the liquid to a boil over high heat, then immediately reduce heat to low to maintain a gentle simmer. Cover the pot with a lid.

Simmer the corned beef gently for approximately 2 hours and 45 minutes (about 50 minutes per pound), checking occasionally to ensure the meat remains submerged.

After 2 hours and 45 minutes, add the potato halves and carrot pieces to the pot. Continue simmering for 20 minutes.

Add the cabbage wedges to the pot, pressing them gently into the liquid. Cover and simmer for an additional 15-20 minutes until the cabbage is tender and the potatoes are easily pierced with a fork.

Check the corned beef for doneness by inserting a fork into the thickest part—it should slide in easily and the meat should feel very tender. Internal temperature should reach at least 145°F.

Remove the pot from heat. Transfer the corned beef to a cutting board and let it rest for 10-15 minutes.

While the meat rests, use a slotted spoon to transfer the vegetables to a serving platter. Cover with foil to keep warm.

Slice the corned beef against the grain into 1/4-inch thick slices. Cutting against the grain is crucial for tender bites.

Arrange the sliced corned beef on the platter with the vegetables. Garnish with fresh chopped parsley.

Serve immediately with whole grain mustard, horseradish sauce, and crusty bread. Ladle some of the cooking liquid over the meat and vegetables if desired for extra moisture and flavor.