It will be a mighty 'lucky' group who gets to eat this corned beef on St. Patrick's Day. A spicy and fork-tender treat. My Mother was Irish and she cooked it this way. I'm married to an Irishman, I'm a Lucky Lassie to have him, and he loves this dish!
Pour beer into a roasting pan and add contents of corned beef seasoning packet, dry mustard, salt, and black pepper to the beer. Stir to combine. Use a sharp knife to pierce corned beef all over; insert garlic slivers into holes. Push whole cloves into meat. Lay the corned beef into the roasting pan.
Bake in the preheated oven for 1 hour; scatter carrots around corned beef and roast for about 1 1/2 hour more. Distribute red potatoes around the meat and roast until corned beef and vegetables are tender, about 40 minutes more.
Place a steamer insert into a saucepan and fill with water to just below the bottom of the steamer. Bring water to a boil. Add cabbage wedges, cover, and steam until tender, about 10 minutes. Transfer to a platter and season with salt and black pepper. Let butter melt over the hot cabbage. Cut visible fat from corned beef and serve with cabbage, carrots, and potatoes.
The garlic amount is very individual. The whole cloves will be stronger than the powdered, but both are strong. Don't use more than 6. The cabbage is cooked separately so it can maintain its subtle taste. Check the tenderness of vegetables and turn heat up if not cooking fast enough.