Corned Beef and Cabbage

Name: Corned Beef and Cabbage
Ingredients: 5 pounds corned beef; 5 garlic cloves, lightly smashed; 10 peppercorns; 4 sprigs fresh thyme; 2 bay leaves; 12 ounces stout (recommended: Guinness); 1 cup beef broth or stock; Water, for simmering; 4 yellow onions, cut into wedges, plus 1 medium yellow or sweet onion, sliced; 2 parsnips, peeled and cut into large chunks; 3 carrots, peeled and cut into large chunks; 6 medium red potatoes, scrubbed; 1 medium head green cabbage, cut into quarters, core removed; 4 tablespoons butter