BROOKLINE — Roast leg of lamb with spring vegetables is the type of special-occasion dish that chef Jeremy Sewall loves to cook in his restaurants and at home. He calls this presentation of tender lamb, asparagus, fava beans, peas, and mushrooms “a spring awakening” that captures the best tastes of the season.
In the kitchen of Lineage in Coolidge Corner, which he has co-owned with his wife, Lisa, for seven years, Sewall admits that “lamb isn’t something that we cook every day at home.” It’s not just that the meat is expensive. It takes time, especially with his “low and slow” technique, which results in a roast with a brown crust and a moist, medium-rare interior. The chef uses this method for fish, and for other meats, not just the lamb that is the centerpiece of many Easter tables. It will also be on the holiday menu in Sewall’s Wellesley home.
“When you cook at high heat, the protein seizes,” he says. “If you give it the time to roast slowly, you end up with a far better product.” Sewall sears a boneless rolled lamb leg on the stove top, then transfers it to a very low oven — set at 250 degrees — to finish cooking, which takes 1 to 1½ hours. Unlike high-temperature roasting, this method is forgiving. It doesn’t need to be timed to the minute, making it ideal for guests. A version of the dish is served as a special at Lineage, where the meat is roasted in the restaurant’s wood-fueled oven.
“When you’re having people over for a holiday, you want to enjoy what you’re supposed to be enjoying — that’s the people you’re with,” says Sewall, 42, father of three, and co-owner of Island Creek Oyster Bar and Row 34, who also oversees the kitchens at Eastern Standard and The Hawthorne and teaches in the Culinary Arts program at Boston University. The advice from this busy restaurateur: “Do as much ahead of time as you can.”
The lamb and vegetable dish was created with that in mind. For six people, Sewall begins with a 5-pound boneless lamb leg. He advises ordering a boned roast that is ready to cook.
Placing the boned leg fat side down, he trims away sinew, bits of bone, and extra fat, seasons the meat with salt and pepper, and rolls it to create a roast even in thickness. He then ties it in five places with butcher twine, starting at the center and working toward the ends. Of the simple knots he uses, Sewall says, “You’re not wrapping a Christmas present.” He browns the roast on the stove top in a large, heavy skillet over high heat before transferring it to a roasting pan to finish slowly in the oven. The roasting time (60 to 90 minutes) depends on the size and thickness of the meat. When an instant-read meat thermometer registers 125 to 130 degrees, the leg is medium-rare and ready to come out of the oven.
At Lineage, Sewall typically uses lamb from Colorado or a farm in New England. “Local lamb is always my preference,” the chef says. “It has more depth and a little more character.” Many markets carry New Zealand and Australian lamb, which tends to be lower in price. “It’s going to taste a little different. There’s no real hard-and-fast rule about what’s better. Try out different things and find out what you like,” Sewall advises. To help understand your preferences, he also suggests asking questions about where the lamb was raised and what it was fed.
As the lamb roasts, Sewall readies the vegetables. He trims the woody ends from thin asparagus spears and blanches them in boiling water for about half a minute, cools them in an ice bath, and drains them. “There’s something about cooking in the spring when you can taste these bright, green vegetables,” Sewall says. He repeats the process with shelled peas and fava beans, removing the outer skin from the favas after they cool. The vegetables can be blanched earlier in the day and refrigerated until it is time to assemble the dish.
Sewall also prepares fingerling potatoes, halving them, then browning them in a cast iron skillet in oil and butter. He tops the potatoes with sprigs of rosemary and finishes them in the oven. Do this while the lamb is resting after roasting, he says.
The dish is assembled “in a last few feverish minutes.” For a final spring touch, he roasts oyster mushrooms. To heat the vegetables before serving, he steams them quickly in a skillet with a bit of water and butter and adds pea tendrils during the last few seconds.
The sliced lamb is set on a platter next to the potatoes and vegetables and the presentation is striking. “It’s not that hard and when you put it in front of people for dinner, it looks great,” he says.
Following his own advice about preparing ahead, Sewall says he will serve an extra leg of lamb he has left from this cooking lesson later that night to cookbook author and TV personality Jacques Pepin and other friends who will be dining at Lineage.
The chef even plans to get out of the kitchen and join them.