Sous vide leg of lamb

23 December 2017

Sous vide leg of lamb

I’m not sure why, but something possessed me to buy a leg of lamb the other day. It was on offer at half price - that might have had something to do with it. But there are times when you rebel against the tiny portion buying you have to do when you’re not feeding large numbers of friends or family and you just want to buy a great big something. 

And regardless of the fact that very soon I’ll be cooking another great big something - namely a big, fat free-range goose - I was moved to get me that leg when I saw it.

One of my few expensive kitchen luxuries is a Sous Vide Supreme that I bought - ooh - ages ago. Long enough ago that I assumed that by now, every kitchen would have one. And I’ve used it often - mostly for sous vide steak (perfect medium rare all the way through, guaranteed, every time), chicken breast and, occasionally, salmon “mi-cuit” - just cooked. But I also have long fancied using it for a great big something - where you put the meat in the waterbath and leave it there for 24 hours.

So I quickly decided I would sous vide this leg of lamb. Just one problem. It’s big. I didn’t have a sous vide bag large enough to contain it. 

A quick diversion for the benefit of the sous vide uninitiated. The sous vide process involves taking your food, placing it in a specially made bag and extracting all the air out with a vacuum machine, before sealing the bag shut. The bag then goes into a precision temperature-controlled water bath at exactly the right temperature.

Suppose you get the perfect medium rare steak when it reaches 57ºC at the centre. You put your steak in a vacuum-sealed bag and plonk it into the waterbath at exactly 57ºC. The temperature can never go above that temperature. Even if you forget it and leave it in the waterbath for an extra half hour, it won’t overcook. And it will be exactly medium rare all the way through. Just sear the steak on a very high heat quickly to get the charred flavourful bits, and you’re very, very good to go.

However. I don’t have leg-sized sous vide bags. But then it came already vacuum sealed in a plastic bag. Why not simply use that to sous vide it? That was what I did - but there’s a cost to doing it that way. It meant that I couldn’t add anything. If you’re slow-cooking a piece of lamb like this, you’re meant to coat it with something like mustard, or at the very least a load of rosemary and garlic. Cooked simply on its own you won’t get any nice added flavours, but perhaps more importantly for some you will find the meat develops a more ‘gamey’ flavour and smell. At least, that’s the received wisdom.

So it was an experiment. Sous vide the lamb “nude” and see if the flavour is too strong and gamey, or if it’s all OK. I mean, I eat plenty of game so how bad can it be?

So I set the waterbath to 54ºC, which would give me lamb that was nicely pink but beautifully cooked, and dropped the lamb in there and went about my business.

A few hours later, I checked on it quickly, and saw that some air had appeared in the bag, and part of the lamb was floating above the surface of the water bath. No problem, I added a small object that was heavy enough to push it down. It’s not ideal that there’s part where there’s air between the meat and the bag - the whole principle of sous vide is that water conducts heat more effectively than air. But it’s in there for 24 hours. The heat is going to get through the whole leg no problem in that time.

The next morning I looked at it, and it wasn’t pretty. At some point, the supermarket shrink wrap bag had developed a leak. The waterbath water was cloudy, with some little globs of fat floating on the top. Still, less than ideal though this was, it would probably still be fine.

At the end of 24 hours, the lamb came out and was finally removed from the bag. Cooked, but pasty - as expected. I scored the skin and, rather belatedly, threw some rosemary at it. Then coated it with oil and seasoned it, before throwing it into a hot hot oven - 200-220ºC. It was in the oven for about 20 minutes in total, developing a nicely browned skin to add that final element of flavour.

That lamb was served with a tomato sauce - aubergines, red onion and potatoes which had been part cooked, and then finished off in the oven with the lamb, added to a tomato base with garlic, anchovies and a little chilli. 

The lamb was beautiful. The meat was tender and juicy as anything. The flavour was good. As it sat there in the middle of the table while we were eating, you could certainly pick up the gamey smell. It was quite strong, for sure. But the meat itself was fine.

Slow cooked lamb salad

So then I was left with a load of lamb to use up. That was yesterday - today I used some to cook Heston Blumenthal’s slow-cooked lamb salad with giant couscous. It uses the Ras-el-Hanout spice mix, along with pomegranate seeds and giant couscous. I needed to get some lamb stock to use with it, since the leaky bag had left me with no cooking juices to speak of. It’s a great plate of food, with multiple layers of flavour. Like a number of the Heston ones, that flavour comes only as a result of quite a bit of multiple faffing around. But at least I already had my slow-cooked lamb, so that did cut the prep time by about four hours.

The rest of the meat will be removed from the bone and frozen. Boxing day, I have a Lamb Bhuna planned.

The Heston recipe is from Heston Blumenthal at home. It's one of the cookbooks I keep coming back to.