Method

• Peel the new potatoes. Parboil for 3 minutes in salted water, drain and set aside.
• Preheat the oven to 200°C/gas 6. Rub the leg of lamb with a little oil, salt and pepper. Peel 3 cloves of garlic and cut in half lengthways.
• Make six incisions in the leg of lamb and insert a piece of garlic and a small piece of rosemary into each one. Break up the rest of the garlic without peeling. Place the lamb in a hot roasting tray with the rest of the oil and sear over a medium heat until golden on all sides. Add the butter and continue to heat until foaming. Put the parboiled potatoes, pearl onions, and the rest of the garlic and rosemary into the foaming butter around the lamb. Season and put in the oven for 10 minutes.
• Turn the potatoes and onions occasionally and baste the lamb with the fat. Turn the oven down to 190°C/gas 5 and continue to cook for 45-60 minutes.
• Take the meat and vegetables out of the pan and keep warm. Pour out most of the fat and add the wine, followed by 200ml of water.
• Bring to the boil and scrape the tray with a spatula to lift the roasting sugars. Continue to boil and add any juices that have run from the leg of lamb. When reduced by half, whisk in a knob of butter, then pass the sauce through a fine sieve. Serve with the lamb and vegetables.