You may be a neophyte when it comes to roasting lamb, but the custom of serving this dish has been around for about 10,000 years. England's King Henry VIII enjoyed lamb with all six of his wives and the versatile animal was prized throughout Europe for providing families with meat, cloth, butter and cheese. Hernando Cortés took sheep to the Americas during Spain's colonisation. Do your part to return lamb to the forefront of culinary favour by serving this recipe to 12 appreciative guests.
Choose between two popular methods of cooking before you begin: Cooking legend James Beard believed roast lamb should be cooked very slowly from start to finish at 162 degrees C (325 degrees F), while others swear by the process that starts with high-heat searing -- 218 degrees C (425 degrees F) -- then reverts to slow cookery for the remainder of the time. Your lamb. Your call.
Select a great cut of meat. If you're not feeling confident about your lamb-buying skills, your butcher will be happy to help you select the right-sized cut to feed your guests. Pick up any lamb cooking tips he or she may share with you.
Mix a flavourful marinade. Put 118 ml (1/2 cup) orange juice, 237 ml (1 cup) white wine, 3 cloves of minced garlic, fresh thyme and rosemary (1 to 2 tsp each to taste), 1/4 tsp ground black pepper and 2 tbsp olive oil into a blender. Alternately, substitute lemon for the orange juice. For a more intense herbal presence, omit herbs from the marinade and tuck the herbs and garlic slices directly into tiny cuts in the meat. Whichever method you prefer, finish the marinade by pulsing the mix in short bursts until blended.
Prep the lamb for cooking by sealing the meat and marinade into a plastic roasting bag. Use a second bag or pan to contain leaks. Allow the lamb to marinade overnight in the refrigerator. Turn occasionally to make sure the meat bathes in flavourful juices. Remove the lamb from the refrigerator around half an hour before you plan to begin cooking it.
Preheat the oven to 218 degrees C (425 degrees F) if you plan to use the searing method or 162 degrees C (325 degrees F) if you're opting to slow cook the lamb. While the oven warms up, remove the meat from the bag and pat it dry with paper towels before placing it on a roasting rack, fatty side up. Set the rack into the pan to collect savoury drippings. Rub with salt and pepper. Put the meat thermometer into the lamb before transferring it to the preheated oven.
Place the leg of lamb into the middle of the oven for the best roasting position. If you are using the searing option, you may wish to add a cup of water to the dripping pan so fat drippings don't smoke when they hit the metal. Sear for 20 minutes. Reduce the temperature to between 148 degrees C and 162 degrees C (300 degrees F and 325 degrees F) for an hour at 10 to 12 minutes per 454 g (1 pound) of lamb. Add extra time if you've left the bone in the meat.
Check the meat thermometer several times. For a medium rare leg of lamb, the reading on the thermometer must reach between 54.4 degrees C and 57.2 degrees C (130 degrees F and 135 degrees F). Continue to cook until the meat is to your liking, but it's strongly recommended that you avoid a well-done leg of lamb as the meat will dry out and the taste will leave something to be desired.
Cool down the meat before removing the string and carving. Collect the drippings for gravy and serve the dish with mint jelly.
Gourmet chefs stress the importance of medium rare leg of lamb preparation, but pay strict attention to your meat thermometer to avoid risking your health as a result of undercooked meat.