Roasted Lamb Shoulder Stuffed with Merguez and Swiss Chard

Marinate the Lamb: Spread the lamb open on work surface. Score the inside of the meat with a paring knife, making incisions every 3/4 inch and taking care not to cut all the way through the meat. Rub inside of lamb with 1 tablespoon oregano and 1 tablespoon pepper. Turn and rub outside with remaining tablespoon of oregano and tablespoon pepper; drizzle outside with olive oil. Transfer to a rimmed baking sheet, cover, and refrigerate for 1 hour.

Make the Merguez Stuffing: Bring a large pot of salted water to a boil. Prepare an ice-water bath. Add chard leaves and cook for 1 minute. Using a slotted spoon, immediately transfer to ice-water bath. Cool, drain, and squeeze out excess water; coarsely chop. Chop enough of the chard stems so that you have 1 cup chopped; discard any remaining stems.

Heat 2 tablespoons olive oil in a large skillet over medium heat. Add onion and cook, stirring, for 1 minute. Add garlic and chard stems; continue cooking until onions are translucent and garlic is fragrant, about 3 minutes. Transfer onion mixture to a medium bowl; set aside.

Heat remaining 2 tablespoons olive oil to skillet and increase heat to high. Crumble sausage into skillet and cook, stirring, until sausage is brown, 2 to 3 minutes. Add chard leaves, reserved onion mixture, rosemary, and thyme; stir to combine. Add panko, lemon zest, mint, and parsley; remove skillet from heat and season with salt and pepper. Spread stuffing on a rimmed baking sheet and let cool.

Roast the Lamb: Preheat oven to 350 degrees. Season lamb with salt and bring to room temperature.

Spread the cooled stuffing over the scored side of the lamb. Loosely roll, like a jelly roll; using 5 pieces of kitchen twine, tie lamb at even intervals to secure stuffing.

Heat canola oil in a roasting pan over high heat. Add lamb to pan and cook, turning, until browned on all sides, about 2 minutes per side. Turn lamb so it is seam-side down in roasting pan. Add lemons, shallots, garlic, thyme, and rosemary to pan and transfer to oven. Roast lamb for 20 minutes, turn, and continue roasting 10 minutes more for medium. Transfer lamb to a cutting board, reserving juices in pan, and loosely cover with parchment paper-lined aluminum foil; let stand for 10 minutes.

Place the roasting pan on the stove over medium heat. Add 1/2 cup water and lemon juice and cook, scraping up any browned bits with a wooden spoon, about 2 minutes.

Remove twine from lamb and, using a sharp carving knife, cut lamb into 12 slices. Arrange on a platter and garnish with lemon, shallots, garlic, thyme, and rosemary from roasting pan. Spoon pan juice over lamb and serve immediately.