Place the corned beef brisket in a large Dutch oven.
Add the garlic, corned beef seasoning, and beef broth (and Guiness beer if using) to the pot.
Bring the mixture to a boil over high heat. Once boiling, reduce the heat to medium-low and let it simmer.
Cover the pot and cook for about 45 minutes per pound, approximately 2 hours for a 2.5-pound brisket, or until the internal temperature of the corned beef reaches 190-205°F (88-96°C).
Add the carrots, baby red potatoes, and cabbage wedges to the pot. Continue to cook for an additional 15 minutes, or until the potatoes are tender.
Carefully remove the corned beef from the pot and let it rest for 15 minutes.
Slice the corned beef against the grain into thin slices. Serve the sliced corned beef with the cooked vegetables. Ladle some of the cooking stock over the meat and veggies for extra flavor.