Place onion and garlic in a large roasting dish. Without removing the skin, trim the duck of excess fat (see note*) and cut a few slashes into the leg. Wrap a slice of pancetta around each duck shank, sprinkle with cumin, salt and pepper and place on top of onions. Roast at 200C for 30 minutes and drain off fat from the pan. Nestle small bunches of grapes amongst the duck legs and pour pinot around. Roast a further 30 minutes until skin is crisp and pan juices have reduced. Serve with confit potatoes* and steamed green beans.
*Rather than discarding the excess fat, roast at 200°C for 20 minutes to render the duck fat, strain and use to pan fry or roast sliced potatoes to accompany the duck – delicious!