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.