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1
Place the lamb on a rimmed baking sheet lined with foil.
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2
Make the marinade: Combine 2 tablespoons mustard, the white wine, garlic, 1 teaspoon salt, 1/2 teaspoon pepper and the thyme in a bowl.
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3
Pour over the lamb, then cover the lamb with plastic wrap and place in the refrigerator to marinate for a few hours or overnight, turning the lamb from time to time.
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4
Preheat the oven to 425 degrees F. Remove the lamb from the marinade and place fatty-side up in a roasting pan fitted with a rack (reserve the marinade).
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5
Season on all sides with salt and pepper and rub with the olive oil.
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6
The bone should be elevated off the bottom of the pan; this will allow for more even roasting.
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7
Place the roasting pan in the center of the oven and roast 25 to 30 minutes.
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8
Reducethe oven temperature to 350 degrees F and continue roasting until an instant-read thermometer inserted into the thickest part registers 140 degrees F, 50 minutes to 1 hour 20 minutes more.
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9
(I usually count between 12 to 14 minutes total roasting time per pound of meat, including the weight of the bone.)
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10
Remove from the oven and let the roast rest fat-side down on a cutting board to help redistribute the juices, about 30 minutes.
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11
Save the pan drippings.
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12
Meanwhile, make the gravy: Scrape the browned bits from the bottom of the roasting pan; transfer the drippings to a small saucepan.
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13
Add the reserved marinade, the sherry and the remaining 1 tablespoon mustard and bring to a boil; cook over medium-low heat, whisking, until thick, about 5 minutes.
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14
Transfer to a gravy boat.
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15
Slice the lamb against the grain and serve with the gravy.
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16
Photograph by Kana Okada
