1. To make the topping, boil the potatoes in a large saucepan of lightly salted water until almost tender, about 15 minutes. Add the leeks and cook until the potatoes are tender, about 5 minutes longer. Drain well and return to the saucepan.

2. Mash the potatoes and leeks together. Return to low heat and stir in the milk and butter. Season with salt and pepper. Remove from the heat.

3. Meanwhile, make the filling. Preheat the oven to 400°F (200°C). Cook the lamb in a large frying pan for 5 minutes, stirring to break up the meat, until lightly browned. Pour off the fat. Transfer the lamb to a bowl.

4. Heat the oil in the frying pan over medium heat. Add the onion and garlic and cook, stirring often, for about 4 minutes, or until softened. Add the carrots. Return the lamb to the frying pan.

5. Add the wine, increase the heat to high, and cook for 3 minutes, or until the wine has evaporated. Stir in the flour, then the stock, parsley, Worcestershire sauce, and rosemary. Bring to a boil, then reduce the heat to low and simmer for 5 minutes. Season with salt and pepper.

6. Spread the filling in a baking dish and cover with the potato topping. Place on a baking sheet and bake for 30 minutes, or until the topping is golden. Let stand 5 minutes, then serve straight from the dish.

Variation

Cottage Pie

Virtually the same dish made with beef, rather than lamb. For a cottage pie, follow the recipe above, but substitute ground round for the lamb, 1 cup fresh or frozen peas for the carrots, and thyme for the rosemary. If you wish, omit the leeks from the topping and stir 2 tbsp prepared horseradish into the potatoes instead