Lamb is one of my favorite meats to cook because it’s one of the hardest meats to perfect. It can easily be overcooked, under seasoned (leaving a heavy gamey flavor in the meat) or poorly cut (you end up chewing through fat and muscle more than meat).
Julia Child has a few marinade recipes that work for lamb, but I think the marinade matters less than the cooking method. If you’re making an entire roasted leg of lamb, I’d suggest studding the lamb with garlic cloves – this imparts a great flavor to the meat, without being too strong. Just take a knife, stab the meat and put cloves into each hole. The garlic cloves are pretty well caramelized and edible after roasting, too! You can see the garlic cloves in the meat in this photo:
Cooking method best summed up by Simply Recipes:
Preheat oven to 425°F. Arrange two racks in the oven – a middle rack to hold the lamb, and a lower rack to hold a roasting pan with which to catch the drippings. Place the empty roasting pan in the oven while the oven is pre-heating. Note that this arrangement of racks and pans, with the roast sitting directly on the oven rack, will create a natural convection of heat in the oven, causing the roast to cook more quickly than if cooked the traditional method in a rack in a roasting pan.
Roast at 425°F for 20 minutes. Then reduce the heat to 300°F and roast an additional hour (for a 6 pound roast), about 10-12 minutes per pound.
In the lower pan, put some fingerling potatoes tossed in olive oil. The drippings will give the potatoes flavor and make the outsides crispy. These are the best potatoes I’ve ever had.