Chef John Kowalski of The Culinary Institute of America demonstrates the technique for deboning a leg of lamb. Basically, the goal is to cut out the large bones while retaining the maximum amount of meat. He begins with the top part of the bone away from him and cuts around the bone, toward and around the "H" bone. He opens up the socket, sees the joint, then cuts right through that joint. Once he removes that bone, he keeps it for another use.
Next, he turns the leg around so the bone is facing away from him, then cuts across the second knuckle joint and around it, trying to lift the bone up at the same time. He cuts along the seam, cutting into the top round, the tender piece of the leg. (He takes off the end piece, which has a lot of collagen and isn't ideal for roasting.) At this point, if you see big chunks of fat, trim them out.
Lastly, he turns the roast over so that the thick fat layer is on top, then begins trimming off the excess fat. You don't want to trim off all of the fat, since it's necessary to keep the meat moist and flavorful, but definitely reduce the thickness.
To tie the roast, first roll it up by tucking the flaps in as you roll it up like a jelly roll, then tie it at even intervals with butcher's twine. Make a loop under the roast near the middle, then bring the twine up and through the loop. Whether it takes four or six ties -- it will depend on the size of the roast -- make the intervals as uniform as possible, since you want the roast to cook uniformly. To finish, run the string lengthwise around and under your previous ties, bring it up and finish it off with another slipknot.
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Hi, I'm Chef Kowalski from the Culinary Institute of America, and I'm going to show you this kitchen basic: how to bone and tie a leg of lamb.
We're going to face the top part of the leg with the shank part away from us, and we're going to begin with the bottom part. We're going to go right around the bone here, and there's a bone that extends inwards; we're just going to slide the knife right along that bone toward the H-bone and around the H-bone. There's a little section here with a hole, and there's meat in there. We want to put our finger in there so we can pull this product forth. We get our knife all the way around that bone, open up the socket a little bit here - there's a joint, and we want to get our knife in there so we can go right through that joint. There's a little cartilage that holds it together, pulling back on the bone and running a knife right around the bone on the other side - trying to keep as much meat off the bone, of course, so we don't waste any. This is really good because you can pull with your finger here and it opens the seam up a little bit, where you can just take that bone out. We're going to put that off to the side; that's a fairly good-sized bone. You can use that in a sauce, and you can also chop it up a little bit into smaller pieces.
At this point we've exposed the bone a little bit. What I like to do is take this, and turn it around so the opening is facing away from you - and now we have a better angle to follow along the bone. Now we come across the second joint. This is a knuckle. We're going to go right around the knuckle here, trying to lift the bone up at the same time so we can pull it away from the meat and loosen it up a little as we cut. Now we have the knuckle; this part of the meat, what we have here, you can buy at the store for osso buco; you'd cut it in maybe three or four inch lengths and braise them.
Here, all we're doing is following the seam. If you move your fingers around, you can loosen the meat; notice these chunks of fat inside. This section would be a top round, and that's the tender part of the leg. We take out this chunk of fat, and the end piece here has a lot more collagen in it, a little bit tougher but still not too bad - you can use it for roasting. I personally like to take that off because I either use it in sauces or braise that a little bit later; it's a much better product for that. Now we're getting down into smaller pieces of the lamb we have left behind. Notice we have another piece of fat here; we'd like to get as many of these pieces of fat out as we can. We also have the other section here. We're going to once again turn this leg around to make it much easier for us to handle. We continue with the next section, rolling our fingers around and just pulling this fat out a little bit.
Now we're just going to turn it over onto its other side. You notice there are a lot more fat segments here on the bottom part, and we want to clean some of that off, so it looks much more palatable. I think this is a good amount of fat we have left here. In cooking, most of this will melt as you're cooking it, probably leaving you an eighth of an inch afterward, at most.
So here we have the product nicely deboned and cleaned, and what we like to do is take this flap and roll it on the inside, and we're simply going to tuck this almost jelly-roll style, if you're making a jelly roll - rolling it up. You can take this flap and tuck it under if you wish. Turn it sideways, clean off the cutting board a little bit, and then we're going to take a butcher's twine. Run it under the roast with the short end away from us, and bringing it up we loop around, up and then through this little loop. Slide this fairly tight. Now I can take the excess string here and I make a loop; as I make that loop I pull the back part up, pull up the slack here, and then we tighten it up. Not too tight but so it's kind of snug. It may take four times or six times, depending on the size of the roast. We try to do this as uniformly as we can. The reason we make this as uniform as possible is that when you're cooking it, you'd like this product to cook uniformly all the way through. When we get to the end, we'll probably take the string about a length and a half of the roast, cut it, and now we go to the bottom part of the roast, and we'll go around and back under the looped strings to hold it as evenly spaced as possible, and also make it fairly snug, so it's firm. We'll tuck the end under, and come up to the top where we're going to now finish it off with another slip knot. We cut the last bit of the string off, and here's your boneless leg of lamb.