I first posted this on eGullet in answer to a question, but I thought I may as well put it on the blog where people can get at it all the time. Next time I do it I'll take some pictures to add.
Lamb is my favorite meat & I've been cooking legs for many years. Here's a pretty much fool proof method that always wows even the non-lamb lovers.
Start in the morning of the day you're going to serve the lamb.
1) read the eGullet culinary institute course on slow cooking meats.
2) Debone the leg end, but leave the shank end as is. This helps both the cooking & the carving.
3) Salt, pepper, a little minced garlic & a little rubbed rosemany should be placed in the boned cavity. Then tie the boned portion back togetherr with kitchen string.
4) cut 3-5 slashes about 1/2 inch deep across the outside leg end on a diagonal. In each slash place an salted tinned anchovy. (Never fear, they add a great flavor & your guests can have a great time guessing, mostly wrongly, what your secret magic ingredient is.) Add a generous amount of freshly ground pepper & some more rubbed rosemary leaves. NO salt as the anchovies take care of that.
5) Here's the only tricky part. Pre-heat an oven to 425 F. Put the lamb in for about 20 minutes to brown. Take the lamb out of the hot oven & place it in an oven at 160 F. The tricky part is getting both temperatures. If you have 2 ovens then you're in great shape. If not then just let the browned lamb rest while you get the oven temperature down to 160 F. DO NOT leave the lamb in while the oven cools down; it will cook too fast.
6) Roast at 160 F for 7 hours. Once you reach 61/2 hours timing is no longer important. Anothe hour or even more will be Ok. This makes life much easier when it comes to bringing the meal together.
7) Let the lamb rest out of the oven for 15-20 minutes before carving.
As an option (but one your guests will love) make a gravy. Carefully pour off most of the fat, but not all, from the roasting tin. Then put the roasting tin over high heat on the stove. Deglaze with a good dollop of red wine. Make sure you scrape all the bits off the sides & bottom. Let boil until the wine is reduced to 1/3 of its original volume. Take the tin off heat & as soon as it quits boiling add lots (8-12 oz) of heavy (35%) cream. Back on heat stirring constantly. Reduce to about 2/3 rds of original volume. Pour gravy into a sauce boat & enjoy.
Lamb done this way is absolutely delicious & has the great advantage of simplicity.
Don't know what you're serving with it, but a couple of recommendations are:
Roast ratatouille & roast potatoes cooked in duck fat with Herbs de Province & lots of sea salt.
STORY: Last time I served this & there were 10 of us; the guests at one end of the table used up most of the gravy. (they'd had it before) not realizing that that was all there was for everybody. Fortunately Tom who is a professional chef was there. He & my wife went back to the kitchen & whipped up more gravy using olive oil, red wine, lamb stock cubes, some leg trimmings & more cream. It was amazingly good all things considered & our guilty guests were saved. Everybody wanted to try the 'concoction', but the guilty paries weren't allowed. Great party!