1 (5-pound) boneless leg of lamb
1 tablespoon beef base
2 cups water
1 1/2 cups port
4 cloves garlic, sliced thin
5 carrots, peeled, sliced in 1/2-inch pieces and cubed
6 stalks celery peeled, sliced in 1/2-inch pieces and cubed
5 parsnips, peeled, sliced in 1/2-inch pieces and cubed
2 white onions, chopped
2 tablespoons chopped thyme leaves
2 tablespoons chopped rosemary leaves
1/2 cup frozen green peas
Mashed potatoes, as needed, for topping
Beer, for serving (recommended: Guinness)