1. Preheat oven to 180°C (350°F). Place the vinegar, ¼ cup (45g) sugar, oil, salt and pepper in a large bowl and stir to combine. Add the lamb and set aside to marinate for 20 minutes.
2. Place the lamb, skin-side up, in a large baking dish. Add the garlic, rosemary sprigs, marinade and stock. Sprinkle the lamb with the remaining sugar, cover with aluminium foil and roast for 2 hours and 30 minutes. Remove the foil and roast for a further 30 minutes or until the lamb is cooked to your liking.
3. Serve with the garlic. Serves 4–6.

Tip: Single-clove garlic is a type of ‘elephant’ garlic. As its name suggests, it has one large clove, rather than a head of garlic that’s made up of a cluster of smaller cloves. Single-clove garlic looks similar to a small onion and is easy to peel. Find it at some supermarkets and grocery stores.