Sous Vide Leg of Lamb With Mint, Cumin, and Black Mustard Recipe (2024)

I tend to prefer bone-in cuts of meat when the bone is easy to work around, as with a prime rib or a juicy roast pork loin. The tastiest bits of meat (read: the fattiest) are typically stuck around the bones.

But leg of lamb is an exception. Not only does the large, irregularly shaped bone make carving neat, against-the-grain slices difficult, it's also a bit too unwieldy to pick up and gnaw on, no matter how uncouth your table manners. Besides, leg of lamb has enough fatty bits that you don't need the ones connected to the bone.

Cooking with a deboned leg of lamb offers another advantage: It's ideal for stuffing and rolling with other ingredients, and because lamb is so robustly flavored on its own, you don't have to be shy or subtle about it. Slow-roasting it using the reverse-sear method is a fantastic way to get perfectly evenly cooked results after stuffing, but today we're cooking sous vide, which is even more foolproof.

A Bold, Crunchy Spice Mix Adds Flavor and Texture

The idea of pairing lamb with crunchy fried spices is one I saw in action when a friend of mine served me a leg of lamb cooked using this great recipe from ChefSteps. It uses a bone-in leg of lamb covered with a heavy dusting of mustard powder, cooked for 24 hours, then served with a coating of fried mustard seed, caraway seed, and herbs. I loved the way the seeds popped against the tender lamb, but I found that after 24 hours of cooking, the lamb was a little too mushy for my taste. (We first theorized that it might have been because he was using a frozen leg of lamb, but I repeated the recipe with a fresh one and ended up with similar results. I don't recommend cooking leg of lamb sous vide for any longer than six hours.)

I start my recipe by heating some oil up in a skillet, then adding a tablespoon of black mustard seeds and a couple of teaspoons of whole cumin seeds. They should immediately crackle and spit (and your kitchen should smell amazing) as they toast. Stirring them continuously will prevent them from burning in spots. Once their aroma has developed, which takes only a few seconds, I transfer the whole mixture to a bowl, season with salt and pepper, and let it cool until it's just cool enough to handle.

Preparing the Lamb for Sous Vide Cooking

A full boneless leg of lamb is large, weighing around 10 to 12 pounds. It's too large to fit comfortably in a sous vide bag, so for this, I recommend using half of a deboned lamb leg, which should be in the four- to five-pound range. Start with a butterflied leg of lamb (it's easiest to just ask your butcher to butterfly it for you—deboning a leg of lamb is not a simple task unless you have a very sharp boning knife and plenty of experience), and spread half of the fried spice mixture all over the interior surface before rolling it back up tightly. When seasoning that spice blend with salt, it's important to remember to add enough salt to season the lamb, not just the spices themselves. It should taste quite salty.

Next, I secure the lamb leg with a few pieces of twine. There's a trick to neatly tying together a rolled roast like this. Tying from one end to the other can push the meat out of shape as it gets squeezed unevenly. Instead, tie it from the outside toward the center, starting with two pieces of twine tied at either end, then working your way inward, alternating sides with each piece of twine to create a nice, evenly cylindrical shape. This helps the whole thing cook and slice more easily as well.

Once it's tied, I season it with salt and pepper and place it inside a zipper-lock bag to cook.

For my recipe, I use the same temperature chart I used for my sous vide rack of lamb, though, because of its larger size, a leg of lamb requires at least two hours to cook through to the center. But, as I mentioned before, any longer than six hours or so will get you into mushy territory, so I recommend capping the cooking time there.

Temperatures and Timing for Sous Vide Boneless Leg of Lamb