The panicky moment: The leg of lamb emerges from the oven. It’s beautiful, but there’s something about it that makes you fearful. Is it underdone? Is it tough? Probably, if you didn’t measure, and instead guessed. The few degrees difference between too-low and just-right can be a matter of pushing it aside or having it dissapears in minutes. Trust your thermometer; not your clock.
One-hundred-thirty-five degrees Fahrenheit is considered to be the right temperature for medium rare for a leg of lamb. But that’s the final temperature, reached via residual heat while meat rests. Pull it at one-hundred-thirty degrees. Let the lamb rest while it cooks further on its own steam, bringing interior temp to the final, ideal degree mark (those last five). By the time the lamb reach one-hundred-thirty-five degrees inside the oven, it’s already in the medium zone. At that point, the juices is starting to thicken. These are called thermal zones, and depending on what you do within those thermal zones, the final texture of your meat will vary wildly.
How to Cook a Perfect Leg of Lamb
The benchmark of medium rare is a nice warm pink inside (juicy); however, when preparing stew or braise it’s totally different. To turn that collagen into gelatin, you really need to get the temperature well past one hundred ninety degrees. This is where connective tissue breaks down completely. That is why the braised lamb fall apart in your fingers, while the roasted lamb stays together. One for another, both have their place; don’t mix ’em up.
Then you think about the cut itself. Boneless roasts, like a rolled leg, has no bone to insulate the interior and cause hot and cold spots, so they cook up more evenly and faster. They’re also easily carved into nice rounds (great if you’re going for a fancy dinner party). Bone-in roasts provide much better flavor because the marrow infuses meat while it roasts. They also hold heat better, which is good for the essential resting period, but they obviously take longer than their size and structure. The chart breaks this down by weight and bone structure. For instance: a 5 pound boneless roast is going to cook differently from a 10 pound bone-in roast.
Beyond the heat, preparation is key: The trickiest step is scoring fat cap into diamonds prior to roasting, which slowly renders out the fat and bastes meat from within. Slits left behind are perfect for slipping in some rosemary sprig and slivers of garlic. Infusing this way makes a roast go from plain to Mediterranean classic. The other reason to score? If you don’t have that layer of fat holding your herb rub in place, you’ll burn it off, leaving no flavor anchors besides the meat itself. Your goal is to get the aromatics deep into lean muscle tissue.
There’s no negotiation on resting the meat. Cover loosely in foil and give it a good rest, at least fifteen or twenty minutes. It lets the juices spread throughout the fibers of meat. Carve right away, and you’ll spill all those lovely flavors onto your cutting board. What’s left? Dry meat. It is a small thing but it makes a difference.
You should of also always cut against the grain. By cutting perpendicular to the muscle fiber, each slice will be tender instead of tough. Let the heat do the work; trust the thermometer, and respect the rest.