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A long time ago, I set about making a big batch of duck confit at home. For months, I saved up rendered duck fat from other recipes, collecting it in dribbles and tablespoons, until I had a couple of quarts' worth. Then I rubbed fresh duck legs with salt, garlic, and herbs; cured them briefly; and finally cooked them, submerged in all that golden fat, at my oven's lowest temperature. I packed them into a big glass bowl, poured the fat on top, and left it to solidify in the fridge. A few weeks later, I boarded a plane to Italy and didn't come back for nearly a year. During all that time, my confit sat in the fridge, encased in its protective fat, with a note on the bowl for the person who was subletting my apartment: "Don't touch."
When I got back, I carefully scraped away at the top layer of fat until I uncovered the first duck leg, then gently excavated it, like an archaeologist digging up some rare antiquity. Roasted in a hot oven until the skin was browned and crisp, the duck blew me away. First, because it really and truly wasn't rotten; second, because it was as tender and silky as I could have hoped for. (Then again, I'd never had sous vide duck confit.)
A few weeks later, my greased hands fumbled that glass bowl of confit, leaving me with a pile of duck, shattered glass, and fat melting between the floorboards.
With sous vide duck confit, I will never be traumatized like that again.
Now, I'm not a sous vide acolyte. I believe the technique is a sometimes-useful tool with notable strengths, but also real weaknesses. It excels if consistency is your ultimate goal—if you want steaks cooked to a precise temperature from edge to edge, for instance. But I often don't want that. I tend to prefer a more robust and deeply browned exterior to my meat, even if it means I have to take a more significant doneness gradient along with it. And, to be honest, in many cases, I prefer that gradient. I'll take a piece of roasted lamb with a range of doneness levels over one with a micro-thin browned band surrounding a soulless, perfectly even medium-rare slab—a texture I find freakishly similar to that of crème brûlée—any day of the week.
Because I have little skin in the sous vide game, believe me when I tell you that it's quite possibly the best way to cook duck confit. Not only does it make an exceptional version of the dish, it's far easier than the traditional method, requiring not an ounce of rendered fat. Imagine: duck confit that you can make right now, with nothing more than duck legs and seasoning. Duck confit that's silkier and more tender than any you've ever tasted. Duck confit that won't ever end up studded with shards of glass, like mine. Now, isn't that something?
A Confit Primer
The confit method of cooking a meat, such as duck, was originally all about preservation. In fact, that's what confit means: "preserved." Farmers in rural southwest France would find themselves with an abundance of meat at the various points in the year when animals were slaughtered—more meat than they could hope to eat before it turned. Their solution was to start by curing the meat with a generous amount of salt, along with seasonings like thyme and garlic, allowing the salt to draw out moisture and lower the meat's water activity.
Next, they would fully submerge the meat in its own rendered fat and slowly cook it over very low heat until tender. This long cooking process yielded meat with an outstanding, almost melting, texture. But that long cook also killed any microorganisms lurking on or in the flesh, because that's what heat does when given enough time.
The final step was to pack the meat into a container, pour the liquefied fat on top to fully submerge it, and cool it down enough for the fat to solidify. This sealed the meat against the air, preventing spoilage. At this point, the confit could be held for months on end, oftentimes without refrigeration; a cool cellar was more than enough. With time, the confit ripened and its flavor changed, becoming deeper, funkier, and more delicious.
A purist would tell you that un-aged duck confit isn't confit at all, that the aging part of the process is essential to a true confit. And, technically speaking, that purist would be right. But the reality is that we no longer have much need for the preservative effects of confit; most of the confit we eat here in the United States hasn't been sitting around for much more than a week or two. Today, confit is enjoyed largely for the texture that the process delivers, even if aging isn't always a part of it.
Sous vide duck confit presents one conundrum here that I need to acknowledge. One could, in theory, cure the duck with an appropriately large amount of salt, vacuum-seal it, cook it for hours on end at a temperature that is high enough (and for a time that is long enough) to kill whatever bad bugs might be in the bags, and then leave the pouches unopened in the refrigerator for several months to age it. One could. But one would be flirting with the very remote yet very deadly threat of botulism, which means that I can't recommend aging sous vide duck confit here or in my recipe. To remain safe to consume, it should be kept refrigerated for no longer than a week or two after cooking, and then it should be eaten.
If that's enough to send the purists away in a huff, so be it. They won't know what they're missing.
Why Sous Vide?
The biggest challenge for most home cooks faced with a duck confit recipe is procuring enough rendered fat to submerge all the duck. Store-bought duck fat is expensive, and making a sufficient amount at home requires a lot of it, and a lot of time—more than most home cooks will find reasonable. You can substitute lard, a totally legitimate choice, but one that imbues the dish with a heavier, porkier flavor compared to duck fat.
Cooking the duck sous vide automatically solves that problem. Because the duck legs are vacuum-sealed, there's little to no air in each bag. As the duck legs cook, the skin renders its own fat, enough to completely envelop the legs in that tight space. You get the effect of duck legs submerged in fat, without needing more than the few tablespoons that form in the bag. (Kenji's sous vide carnitas take advantage of this same principle.)
On top of that, an immersion circulator allows you to cook at temperatures that are lower and far more precise than just about any oven, slow cooker, or other device commonly called for in more traditional confit recipes. That gives us unprecedented control over the meat's texture.
I'd be remiss here if I didn't mention the work of Paula Wolfert, both for popularizing the technique of making confit in the United States and for being generations ahead of most other cooks on the advantages of sous vide cooking. I was recently corresponding with Emily Kaiser Thelin and Andrea Nguyen, author and editor, respectively, of the biography and cookbook Unforgettable: The Bold Flavors of Paula Wolfert's Renegade Life, and they pointed me toward the original, 1983 edition of Wolfert's The Cooking of South-West France, in which she describes the implications of sous vide cooking on page 349. Nineteen eighty-three!
More than two decades later, Wolfert had an exchange with Nathan Myhrvold on an eGullet forum, in which he suggested the sous vide method for confit in particular. Shortly thereafter, she published a recipe for the technique in the 2005 revised edition of the South-West France cookbook.
Wolfert, I've been told by Thelin, ranks sous vide duck confit as a great time-saver, but one that lacks a certain something compared with the real deal. That's how I tend to feel about most sous vide cooking, though, in this case, I think the ease and rewards make up for whatever shortcomings there may be compared with a true, aged duck confit. I've also settled on a temperature and time in my own recipe that are considerably different from Wolfert's—mine is not a time-saver—and I think the textural results are superior enough to make an even more compelling argument in favor of sous vide in this application.
Temperature and Timing
The big questions in developing any sous vide recipe are how hot and how long. The transformation of meat is dependent on both of those factors, and testing all the potential combinations of heat and time can take...time. And a lot of duck.
I ran tests at temperatures ranging from 140 to 170°F (60 to 77°C), and times from eight hours up to 40 hours. For comparison, Wolfert calls for a water bath held at 180°F (82°C), and times ranging from five to nine hours, which adhere more closely to traditional confit conditions. I wasn't able to get great results at 170°F, even in as short a time as eight hours, so I didn't bother trying to push up the temperature to 180°F—all that lay ahead was dryness. Of course, dryness is a relative term here. The 170°F duck, cooked for eight hours, was tender and delicious—just not as tender and delicious as the duck cooked using the settings that I ended up pegging as the ideal combination of temperature and time: 155°F (68°C) for 36 hours.
Here's a description of the results from my tests:
Cooking Temperatures for Sous Vide Duck Confit
|140°F (60°C) for 20 to 40 hours||Firm texture across the time spectrum, more like roast duck. Good, but not like confit.|
|155°F (68°C) for 20 to 40 hours||Incredibly silky and moist; completely fork-tender. The best were the 36- and 40-hour samples, which were difficult to distinguish.|
|170°F (77°C) for 8 to 40 hours||The meat falls from the bone the most easily, but there's a noticeable chalky dryness in the 20- to 40-hour samples. Shorter cooking times produced duck that was slightly drier and less tender than the 155°F samples. A decent option if time-saving is critical; otherwise, not the best.|
In addition to the above temperatures, I also ran tests at five degrees above and below my preferred 155°F sample, just to make sure I wasn't hovering close to, but not exactly on, the ideal temp. The 160°F (71°C) samples were drier than the duck cooked at 155 and 150, while the latter two were indistinguishable from each other. I decided to stick with 155°F, given the slightly superior microbe-killing power of the higher-temperature water bath.
While my sous vide duck confit recipe isn't intended to be aged like a classic confit, I was still curious to know how important the curing step was. To test it, I ran five samples, all cooked at 155°F for 36 hours. My control was seasoned with salt, pepper, garlic, and thyme; vacuum-bagged; and placed directly into a water bath to cook for the set time.
Against that, I tried three different approaches: duck that was seasoned, vacuum-sealed, and left in the fridge for 24 hours before cooking; duck that was seasoned, wrapped in plastic, cured for 24 hours, then vacuum-sealed and cooked for the same duration; and duck that was seasoned, left to air-dry in the fridge for 24 hours, then vacuum-sealed and cooked.
The differences here ended up being extremely subtle. One of three tasters noted that the air-cured duck had a deeper, muskier flavor, which I also noticed (but I wasn't tasting it blind). We all agreed that the duck that had been cured in the vacuum bag for 24 hours was the silkiest of the bunch, but—and I can't stress this enough—the difference was so subtle, almost verging on imperceptible, that I can't rule out the possibility that it was due to variations in the duck legs themselves. In the end, my advice is to either cure the duck in the vacuum bag for 24 hours before cooking, or just cook it straight away without the curing period. You'll hardly know the difference.
Once the duck is cooked, it can be kept refrigerated, in its unopened bag, for one, maybe two weeks. What you do with it after that depends on the recipe. It can be gently rewarmed, then pulled from the bone, shredded, and blended with some of the rendered fat to make rillettes, or broiled or baked in a hot oven until the skin is browned and crispy, then served a million different ways. None of which involve shards of glass—guaranteed.
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