Reverse-Sear Leg of Lamb with Garlic, Fennel and Herbs
- Makes8-10 servings
- Cook Time5 hours
- Active time plus cooling1 hour active
The conventional way to cook a roast or thick steak so it develops a well-browned exterior is to sear it over high heat, then finish it the gentler heat of the oven. The reverse-sear method, which we use here, flips the order. We slow-roast a boneless leg of lamb until just shy of perfectly done, then blast it with high heat for browning. It’s an easy, hands-off method that results in meat with more even doneness from edge to center. We toss sliced Yukon Gold potatoes into the roasting pan under the lamb; they soak up the drippings and become an effortless, delicious side. A leave-in thermometer—the type that allows you to remotely monitor the food’s internal temperature as it cooks—is especially handy.
Don’t forget to allow the roast to stand at room temperature for an hour before cooking. This helps equalize the internal and external temperatures for faster and even more cooking.
Step 1
In a food processor, combine the oregano, rosemary, fennel seeds, peppercorns, pepper flakes, 6 garlic cloves and 2½ teaspoons salt. Pulse until coarsely ground, about 15 pulses, scraping the bowl as needed. Transfer to a small bowl, then stir in the ¼ cup oil, honey and lemon zest.
Step 2
Smear the mixture over the lamb, rubbing it into the meat. Tightly roll up the roast in the same direction as it was rolled when purchased, then secure with kitchen twine spaced at 1-inch intervals. Let stand at room temperature for 1 hour or cover and refrigerate for up to 24 hours. (If refrigerated, let stand at room temperature for 2 hours before cooking.)
Step 3
About 15 minutes before roasting, heat the oven to 250°F with a rack in the lower-middle position.
Step 4
In a large (roughly 12-by-15-inch) roasting pan, toss the potatoes, the remaining 4 garlic cloves and the remaining 1 tablespoon oil. Distribute in an even layer, then add ½ cup water. Place the lamb on a V-style rack and set in the roasting pan. Roast until the center of the thickest part reaches 115°F, 1¾ to 2¼ hours.
Step 5
Remove the pan from the oven and increase to 450°F. Carefully transfer the rack with the roast to a rimmed baking sheet. Stir and flip the potatoes, then distribute in an even layer. Place the lemon halves cut sides down in the pan (it’s fine if they sit on the potatoes) and add another ½ cup water. Return the rack to the roasting pan and roast until the lamb is well browned and the center of the thickest part reaches 120°F for medium-rare or 125°F for medium, 20 to 25 minutes.
Step 6
Once again, transfer the rack with the roast to the baking sheet; let rest, uncovered. Return the potatoes and lemon halves to the oven and roast until the potatoes are deeply browned, 20 to 25 minutes.
Step 7
Using a wide metal spatula, transfer the potatoes to a platter. Squeeze the juice from 1 lemon half over the potatoes. Transfer the roast to a cutting board. Slice it crosswise ¼ inch thick, removing the twine as you go, and arrange on the platter with the potatoes. Drizzle the accumulated juices from the baking sheet and cutting board over the potatoes. Squeeze juice from the remaining lemon half to taste over the lamb.