Serves 6 to 8
For the stew:
4 tablespoons unsalted butter
2 pounds lean boneless leg of lamb, cut into 1/2 inch cubes
½ pound turnips, peeled and diced
½ pound carrots, peeled and diced
3 celery stalks. trimmed and sliced
1 medium onion, peeled and diced
1 teaspoon fresh thyme leaves
½ cup all purpose flour
2 cups beef stock
1 cup tomato paste
Salt and freshly ground black pepper to taste
For the potato topping:
2 pounds white or red boiling potatoes, peeled and cut into 1 inch cubes
¼ pound (1 stick) unsalted butter
1 egg yolk
1 teaspoon salt. or to taste
½ teaspoon freshly ground white pepper, or to taste.
1. To make the stew, melt the butter in a Dutch oven or large saucepan over medium high heat. Add the lamb and brown on all sides, making sure not to crowd the pan. This may have to be done in batches. Remove the lamb from the pan with a slotted spoon, and set aside.
2. Add the turnips, carrots, celery and onion to the pan, and saute for 3 minutes, stirring frequently, or until the onions are translucent. Return the lamb to the pan along with the thyme, and sprinkle the flour over the lamb and vegetables. Cook over low heat for 3 minutes, stirring frequently, to cook the flour. Add the cold stock or water, raise the heat to medium high, and bring to a boil. Stir in the tomato paste, and season with salt and pepper. Cook the lamb mixture covered over low heat for 40 to 55 minutes, or until the lamb is tender.
3. While the lamb is braising, place the potatoes in salted cold water and bring to a boil over high heat. Boil the potatoes until tender, about 15 minutes. Drain, and then mash the potatoes using a potato masher or hand held electric mixer with the butter, egg, yolk, salt and pepper. Place the mixture in a pastry bag fitted with a large star tip.
4. To serve, preheat an oven broiler. Place the lamb into a large baking dish or individual dishes, and pipe the potatoes into a latticework pattern on the top. Place 6 inches from the broiler element, and brown the potatoes. Serve immediately.
Note: The lamb and potatoes can be prepared up to a day in advance and refrigerated, tightly covered. Reheat the lamb over low heat before piping the potatoes and the final broiling.