Unlike duck breast, duck legs are tough and need low & slow cooking to make them tender. Confit is a traditional French preparation to cook the legs low and slow in duck fat to make them tender as well as preserve them. To make duck leg confit the traditional way, you need quite a bit of duck fat. With sous-vide techniques you can get the same result with only one tablespoon of duck fat for each leg. Unlike other sous-vide preparations, there are no advantages in texture, which is the same as traditional. It is possible to make duck legs tender with sous-vide at lower temperatures (i.e. 62C/144F) with a different texture, but sous-vide confit is cooked at 82C/180F to obtain a traditional confit texture. Apart from using much less duck fat, the advantage is also that temperature control is very easy. Just set your water bath to 82C/180F and it will do the rest for you. Since this was my first experiment with sous-vide duck leg confit, I followed the instructions from Modernist Cuisine.
I started with a pair of duck legs. French/European ducks apparently are smaller than their American counterparts at 250 grams (about 1/2 pound) per leg, rather than the 400 grams (.9 lbs) Moulard duck legs described in Modernist Cuisine.
I packed the cure as evenly as I could on the duck legs, and vacuum sealed them to facilitate the curing process. I followed the Modernist Cuisine recommendation of using 18% by weight cure mix (i.e. 90 grams of cure for 500 grams of duck legs) and a curing time of 10 hours.
I had not adjusted the curing time for the smaller leg size, which I should have because the legs ended up being a bit on the salty side. With the same size of the duck legs, next time I will probably opt for only 6 hours or so of curing.
Then I sealed them into a vacuum pouch again, with a tablespoon of duck fat for each of the legs. (This duck fat was rendered from the duck breasts used for my recent duck breast experiment.)
You can now let them cool slightly and progress to the next step, or cool them quickly in ice water and refrigerate them until you are ready to serve and then reheat 12 minutes at 80C/176F.