Planning to make [this boneless, butterflied leg of lamb recipe](https://www.seriouseats.com/slow-roasted-lamb-garlic-anchovy-lemon-rosemary-food-lab-recipe) for Thanksgiving dinner. The recipe calls for a 10-12lb leg of lamb. If you glance at the comments section, you will see there is some controversy regarding this figure. I’ve called every butcher in my town and they’ve all assured me the largest deboned, butterflied leg of lamb you can get is gonna be between 4 and 6lbs (outside of the one comment about dorper lamb, other commenters have speculated 10-12lbs could be the weight of the leg BEFORE being deboned). This is not a problem as I’m only cooking for four people, but leaves me a little dubious about the proper cooking time. Of course I can just keep an eye on it, check the temp every so often, but I have plenty of other things to cook that day and I’m trying to get everything to hit the table around the same time. Hoping maybe someone here has tried this recipe before and can give me some pointers. Thanks!
by JiANTSQUiD
5 Comments
I’ve done the recipe a couple of times. Just use whatever size you have.
Yeah, I’ve made this recipe several times, it’s excellent. I might do it for Thanksgiving, actually.
I usually have about a 5 lb leg and you definitely need to reduce the cook time. For a 5 lb roast I start checking temperature after about 1 hr 15 minutes or so. Goal is 120° F, pull it out and rest while you crank the oven up to 500° then blast it for about 10 minutes. That should get you to a nice medium rare to medium.
I don’t know why it says 10-12 pounds on the website but the same recipe in my book says 5-7 pounds! The timing should be right if your oven temp is accurate, but always rely on a thermometer, not a timer.
Lamb can also hugely vary in size with imported New Zealand or Australian lamb typically much smaller than American lamb which is larger and fattier typically.
Around me Costco has 8-10 lb legs but generally like the others say what matters is the temp, not the size.
>but leaves me a little dubious about the proper cooking time.
Don’t cook to time, cook to temperature and use time as an estimate. It looks like Kenji is using the reverse-sear method (you could also sous-vide it if you have the equipment), and that’s pretty forgiving as it takes longer to reach temperature thus there’s less of a chance to overshoot your desired temp. For a recommended time, you can use his 3-3.5 hour recommendation and divide it by the weight of your roast compared to his (I would estimate the one in his blog post is ~8-10lbs, so if you’re looking at a 6lb roast you can likely reduce the cooking time by ~25%).
I would cook it at 275F for 2 hours, then start checking the temp every 15 minutes. Once it hits 125-130F (depending on your desired doneness), proceed with the resting then high-heat portion of cooking.