Cooking method:

1. Preheat the oven to 150°C/300°F/Gas 2.
2. Unwrap the lamb and place in a lightly oiled shallow ovenproof dish or small roasting tin. Cover dish with foil and roast for 2½ hours.
3. After 2 hours bring a large saucepan of water to the boil. Add the potatoes, return to the boil and cook for 3-4 minutes until just tender. Drain in a colander under cold running water.
4. Heat oil in a large frying pan and gently fry onion and garlic for 5 minutes until softened.
5. Remove lamb from oven and transfer to a plate. Increase oven temperature to 200°C/400°F/Gas 6. Arrange a layer of potatoes in the ovenproof dish or tin used to roast the lamb. Season with salt and pepper. Top with a layer of onions and garlic. Continue layers until all the vegetables are used.
6. Pour cream over potatoes and return lamb to dish. Bake for 30-45 minutes until the potatoes are pale golden brown and bubbling. Serve with freshly cooked seasonal vegetables.