To prepare the lamb:Place the lamb in a baking dish and coat it well on all sides with the smashed garlic, rosemary, chopped parsley, mint, oil, lemon and cracked black pepper. Cover and refrigerate overnight. Take the lamb out of the refrigerator for 30 minutes before stuffing it, to bring it to room temperature.
To make the stuffing:Toss the breadcrumbs with 2 tbsp rapeseed oil. Spread them on a baking sheet and toast for 6-8 minutes, stirring once or twice, until they are golden brown. Heat a medium pot over high heat for 1 minute. Add the remaining rapeseed oil, the rosemary and the chilli; let them sizzle in the oil about 1 minute. Stir in the shallots, garlic and thyme and season with sea salt and freshly ground black pepper. Turn the heat down to medium and cook about 10 minutes, until the shallots are translucent. Transfer the mixture to a large bowl and discard the rosemary. While the shallots are cooking, heat a medium sauté pan over high heat for 2 minutes. Crumble the chorizo into the pan, and sauté about 8 minutes, until the sausage is crisp and cooked through. Drain the chorizo of excess oil and add it to the bowl with the onions. Stir in the breadcrumbs, mint and parsley and combine well. Taste for seasoning.
To cook the lamb:Preheat the oven to 175°C/325°F/Gas Mark 3. Season the lamb on both sides with sea salt and a little freshly ground black pepper. Lay the meat on a cutting board, fat side down and open like a book. Spoon as much of the chorizo stuffing as you can (about half or a little more) on the right side of the lamb. Fold the left side over the stuffing, as if you’re closing a book. If some of the stuffing falls out, stuff what you can back in. Tie the lamb with butcher’s string at 2-inch intervals to hold it together while roasting. Carefully place the lamb on a roasting rack set in a roasting pan. Put the remaining chorizo stuffing into a small dish and set aside. Roast the lamb for 1 hour and 20 minutes, rest for 20 minutes. While lamb is resting put the rest of the stuffing in the oven and cook for 15 minutes.
To make the spiced shallot and cherry tomato sauce:Heat the oil in the pan and gently fry the shallots for 2-3 minutes, add the garlic, tomatoes, cayenne pepper and cook for 5 minutes or until the sauce has reduced slightly. Stir in the herbs and season to taste.
To serve, slice the lamb and serve with the tomato sauce.
NB You can ask your butcher to bone and butterfly a leg of lamb for you