Roast leg of lamb with tarragon and mint butter

Preheat the oven to gas mark 4-5, 180-190°C, 350-375°F. In a small bowl, mix together the tarragon and mint butter ingredients. Place the joint on a chopping board and make several slits over the surface with a sharp knife. Season on both sides and spread the herb butter over both sides of the joint and into the slits. Transfer the joint to a metal rack in a large non-stick roasting tin and open roast for the preferred, calculated cooking time, basting occasionally with any meat juices. Cover with foil if browning too quickly. Remove the joint from the oven, cover loosely with foil and leave to rest for 15-20 mins. Meanwhile, make the tangy gravy; spoon off any excess fat from the roasting tin and discard. Place the tin over a medium heat and sprinkle over the flour. Stir well with a small whisk or spoon, add a little stock and stir again, scraping the base of the pan to release any rich lamb sediment. Add the remaining stock, orange juice and any meat juices from the lamb plate. Adjust the seasoning if required and simmer for 8-10 mins, stirring occasionally. Add the herbs and strain before serving. Serve the lamb with seasonal vegetables and the gravy.