Peel the garlic cloves and cut them into thin slivers. With the point of a sharp knife make slits all over the shoulder of lamb and push in the garlic slivers as deeply as possible. Season the joint generously.

Heat the olive oil in a large, flameproof casserole and brown the shoulder of lamb on all sides. Remove the joint. To the remaining fat, add the chopped onions and carrot and saute until golden.

Add the stock, chopped tomatoes and tomato puree, and season the vegetables to taste with salt and pepper. Bring to the boil. Return the shoulder of lamb to the casserole and sprinkle with thyme.

Cover the casserole and simmer gently until the lamb is tender, about 1 hour for medium rare.

About 10 minutes before the end of cooking time, add the stoned olives.

When the lamb is tender, transfer it to a heated serving dish. Skim the fat from the sauce and spoon the vegetables and sauce around the lamb. Garnish, then serve hot.