Preheat the oven to 300 degrees F.
Put the lamb in a roasting pan and roast until an instant-read thermometer registers 140 degrees
F, about 2 hours. Remove from the oven to a cutting board and let stand for 2 hours. Trim off the fat and cut into 1/2-inch squares. In a medium pot over medium heat, mix the beef base with the water and bring to a boil. Add the port, reduce the heat and simmer for 15 minutes. While the mixture is simmering, add the garlic. In a large saucepan add the carrots, celery, parsnips and onions. Stir in the lamb and the beef broth mixture and cook until the vegetables are al dente.
Distribute the mixture evenly into 12 shallow heat-proof dishes and sprinkle with chopped thyme and rosemary. There should be about 2 ounces of liquid in each dish, or about a 1/2-inch deep. Sprinkle with green peas. Pipe mashed potatoes through pastry bag to cover the mixture. Raise the oven temperature to 400 degrees F. Put the dishes into the oven and bake until the tops of the mashed potatoes are browned.
Remove from the oven and serve with a pint of beer.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Don Murphy, Murphy's Bar and Grill, Honolulu, HI