Step 1

Preheat an oven to 325°F (165°C). Season the lamb with salt and pepper. In a large ovenproof pot over medium-high heat, warm the olive oil. Working in batches, sear the lamb, turning, until browned on all sides, about 5 minutes. Transfer to a plate.

Step 2

In the same pot over medium heat, melt 4 Tbs. (1/2 stick) (2 oz./60 g) of the butter. Add the onion, carrots, celery and garlic, cover and cook, stirring, until the carrots are crisp-tender, about 5 minutes. Uncover, sprinkle with the flour and stir well. Gradually stir in the broth and wine. Add the rosemary. Bring to a boil over medium heat, stirring to scrape up any browned bits from the pot bottom. Return the lamb to the pot, cover, place in the oven and cook until the lamb is tender, about 1 1/2 hours.

Step 3

About 30 minutes before the lamb is ready, oil a 3-quart (3-l) baking dish. In a saucepan, combine the potatoes with salted water to cover and bring to a boil. Reduce the heat to medium, and simmer until the potatoes are tender, 20 to 25 minutes. Drain well. Return the potatoes to the pan and stir over medium-low heat for 2 minutes to evaporate the excess moisture. Cut 3 Tbs. of the butter into pieces and add to the potatoes. Using a potato masher, mash the potatoes while adding enough cream to create a smooth texture.

Step 4

Season the lamb mixture with salt and pepper, stir in the peas and pour into the prepared dish. Spread the mashed potatoes evenly on top. Cut the remaining 1 Tbs. butter into bits and use to dot the top. With the oven still at 325°F (165°C), bake until the top is lightly tinged with brown, about 20 minutes. Remove from the oven and let stand for about 5 minutes before serving. Serves 6.

Step 5

Adapted from Williams-Sonoma One Pot of the Day, by Kate McMillan (Weldon Owen, 2012)