James Martin’s stuffed leg of Welsh lamb with onion and leek sauce

Method

1. Heat the oven to 240°C/220°C fan/gas 9. Put the lamb skin-side down on a board, then open it out and season.
2. For the stuffing, whizz the parsley and mint in a food processor to chop finely. Add the garlic, breadcrumbs, mustard, hazelnuts and egg. Season and whizz again to combine (or chop everything finely for a coarse stuffing).
3. Spread the stuffing all over the inside of the boned lamb, then scatter over the black pudding and season again. Roll up the lamb to enclose the stuffing, then tie securely with string along the length of the stuffed joint. Put on a rack in a large roasting tin and roast for 30 minutes, then reduce the temperature to 200°C/180°C fan/gas 6 and roast for a further 1 hour. Set aside to rest for 30 minutes.
4. Meanwhile, to make the sauce, heat the butter in a saucepan over a medium heat. Once it’s melted and foaming, add the onion and cook for 5 minutes, stirring regularly. Stir in the leeks and cook for 2 minutes more. Stir in the flour and cook for 30-60 seconds. Season, whisk in the wine, milk and cream, season again, then stir in the parsley.
5. Lift onto a board, then untie the lamb. Slice and serve with the sauce, any resting juices, roast potatoes and seasonal greens.