Cut the garlic in half crosswise. Peel onion and cut into strips. Wash meat, dab dry and rub garlic all around, season with salt and pepper. Wash the rosemary and shake dry. Put leg of lamb, onion, rosemary and garlic in a roasting pan. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for about 2 hours. After approx. 1 hour add 200 ml water
Remove meat and keep warm. Loosen frying set and pour through a sieve. Add stock and wine, bring to the boil and simmer for about 10 minutes. Stir flour and 6 tbsp. water until smooth and thicken sauce with it.
Stir in mustard and jelly. Season sauce with salt and pepper. Serve the meat. Add the sauce