How to Make It
Preheat the oven to 325°. Using a sharp knife, make deep slits all over the lamb and fill each slit with a garlic slice. Season the lamb with salt and pepper.
In a large enameled cast-iron casserole, heat the olive oil. Add the lamb and cook over moderate heat, turning, until the roast is browned and crusty, about 12 minutes. Transfer the lamb to a plate and pour off the fat in the casserole.
Add the pearl onions and cook over low heat until lightly browned, about 5 minutes. Add the wine and scrape up any browned bits from the bottom of the casserole. Add the stock, tomatoes, rosemary sprig and lemon zest strips and bring to a boil. Return the lamb and any accumulated juices to the casserole and cover.
Transfer the covered casserole to the oven and braise the lamb for 1 1/2 hours, until the meat is nearly tender. Add the carrots and fennel wedges, cover and braise for about 45 minutes longer, until the vegetables and lamb are tender.
Transfer the lamb and vegetables to a platter and cover with foil. Discard the rosemary sprigs and lemon zest. Boil the braising liquid over high heat until it is reduced by half, about 15 minutes.
Meanwhile, in a small bowl, toss the parsley with the crushed red pepper flakes, chopped rosemary, minced lemon zest and the minced garlic.
Discard the strings from the lamb and slice the meat. Transfer to a platter and garnish with the parsley-lemon gremolata. Serve with the sauce and vegetables.