1 Season the leg of lamb well on all sides with salt and pepper. Heat the clarified butter, brown the lamb on all sides over a fairly high heat and place in a roasting dish.
2 Add the stock and roast the lamb in an oven preheated to 200°C (180° fan) | 400F | gas 6 for 30 minutes.
3 Wash the rosemary and strip the leaves from the stalks. Divide the garlic bulb into individual cloves. Put the potatoes, rosemary leaves and garlic into a bowl and mix with the olive oil.
4 Add to the roasting dish and roast for a further 30-40 minutes. Then insert a meat fork into the leg of lamb to see if it is cooked: if the juice runs clear the meat is done, if it is still pink, cook for a further 5-10 minutes.
5 Take out of the oven and allow the meat to rest for 10 minutes covered with aluminium foil. Slice the meat across the grain and serve with the potatoes and garlic.