Roast Loin of Lamb with Vegetables and Mint Sauce

For the lamb: rinse and pat dry lamb, score rind in diamond pattern and season well with salt and pepper. Place on a well-greased baking sheet and roast in preheated oven at 160°C (approximately 325°F) for about 40-45 minutes. 15 minutes before the end of roasting, add peeled and diced potatoes and rosemary to the pan. After 7 minutes, add scallions to the pan. Remove pan from the oven, place meat into another pan and season lightly with salt. Increase oven temperature to 270°C (approximately 500°F) and roast meat for about 10-15 minutes or until browned. Remove vegetables from the roasting pan and heat oil in a little pan, toss vegetables briefly and keep warm.  

For the sauce: combine cooking gravy with sherry and strain through a fine sieve into a pot. Add veal or lamb stock and bring to a boil, simmer briefly and add mint, diced tomatoes and garlic, simmer briefly. Remove from heat and add cold butter to the sauce, whisk well.