- 500g (1lb 2oz) sweet potatoes, peeled and roughly chopped
- 1 can anchovies in oil, drained and finely chopped
- 2 garlic cloves, crushed
- 1tbsp rosemary, finely chopped
- 2½tbsp pine nuts, finely chopped
- a bone and butterflied leg of lam (you can ask your butcher to do this), around 1.8kg (4lb)
- olive oil for brushing
Heat the oven to 220C, 200C fan, 425F, gas 7. Bring the sweet potatoes to the boil in a pan of salted water; cook until tender. Drain and set aside to cool, before mashing. Blend the chopped anchovies with the garlic until smooth, mix with the rosemary and pine nuts, stir through the sweet potato mash and season with black pepper.
Spread the leg of lamb out on the work surface, skin side down, and spoon the stuffing down the centre. Roll to make a neat cylindrical parcel and secure with butcher’s string. Place in a roasting tin, brush with oil and cook, uncovered, for 20 minutes in the oven, then reduce the temperature to 190C, 170C fan, 375F, gas 5, and allow to cook for another 45 minutes to 1 hour.
Remove the lamb from the oven and set aside to rest for 10 minutes. Then serve with the pan juices, buttered spring greens and boiled new potatoes.