1.Preheat oven to 180°C/350°F.
2.Dry-fry seeds and spices in a small frying pan over high heat about 30 seconds or until fragrant. Combine spice mixture with half the oil in a small bowl.
3.Using a sharp knife, score lamb at 2.5cm (1-inch) intervals; push garlic into cuts. Rub spice mixture all over lamb; season.
4.Heat remaining oil in a large flameproof dish on stove top; cook lamb, turning, until browned all over. Remove from dish.
5.Meanwhile, peel onions, leaving root ends intact. Add onions to dish; cook, stirring, until browned.
6.Add carrots and the water to dish, bring to the boil; place lamb on vegetables, cover loosely with foil. Roast in oven for 1½ hours.
7.Reduce oven temperature to 160°C/325°F.
8.Remove foil from lamb; roast a further 1½ hours or until lamb is tender. Cover lamb; stand 10 minutes. Strain pan juices into a small heatproof jug.
9.Slice lamb, thinly, serve with onions, carrots and pan juices.
Serve with steamed green beans and roast baby potatoes.Note