To prepare the roasted leg of lamb: Place the butterflied leg of lamb in a baking dish.
In a small bowl, combine the garlic, rosemary, parsley, mint leaves, rapeseed oil, lemon juice and freshly ground black pepper.
Coat the lamb well on all sides with the marinade, cover and refrigerate overnight to marinate.
Take the lamb out of the refrigerator for 30 mins before stuffing it, to bring it to room temperature.
Preheat the grill on high.
For the shallot and chorizo stuffing: In a small bowl toss the breadcrumbs with 2tbsp of rapeseed oil. Spread them on a baking sheet and toast under the grill for 4-8 mins, stirring once or twice, until they are golden brown.
Heat a medium saucepan/pot over a high heat for 1 min. Add in 2tbsp rapeseed oil with the rosemary red chilli and let them sizzle in the oil about 1 min. Stir in the shallots, garlic and thyme leaves and season with sea salt and freshly ground black pepper. Turn the heat down to medium and cook for about 10 mins, until the shallots are translucent. Transfer the mixture to a large bowl and discard the rosemary.
Meanwhile heat a medium sauté pan over a high heat for 2 mins. Crumble in the chorizo and sauté for about 8 mins, until the sausage is crisp and cooked through. Drain the chorizo of excess oil on a sheet of kitchen roll and add it to the bowl with the onions in.
Stir in the breadcrumbs, mint and flat leaf parsley and combine well. Taste for seasoning.
To cook the roasted leg of 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. Put the remaining chorizo stuffing into a small dish and set aside.
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.
Roast the lamb for 1 hr and 20 mins, rest for 20 mins.
While lamb is resting put the rest of the stuffing in the oven and cook for 15 mins.
For the spiced shallot and cherry tomato sauce: Heat the rapeseed oil in the pan and gently fry the shallots for 2-3 mins, add the garlic, cherry tomatoes and cayenne pepper then cook for 5 mins or until the sauce has reduced slightly. Stir in the mint and chives and season to taste.
To serve, slice the lamb and serve with the tomato sauce.
