Whenever I buy a whole chicken, I always prepare the legs and the breast separate because otherwise I end up with a dry breast or undercooked legs. I recommend to buy a free-range chicken, but don’t spend your money on a very expensive breed. The cheapest free-range will do (and in most cases will taste just the same).
The legs I rubbed with salt and freshly ground black pepper and sealed into a vacuum pouch. Then I cooked sous-vide for 12 hours at 62C/143F. This temperature is slightly lower than the desired core temperature at the end of cooking, that is because the skin will be crisped under a very hot broiler and thus the meat will be cooked slightly more from that treatment.
When they came out of the sous-vide waterbath, I patted them dry with paper towels and rubbed slightly with olive oil. Then I put them closely under a very hot broiler. This way, the skin can crisp as soon as possible without overcooking the meat underneath more than strictly necessary. Please note that I put a baking sheet with some water underneath to catch any drippings from the chicken. Using the water prevents the dripping fat from burning, which is hard to clean.
As soon as the skin was nice and brown, after just a few minutes, I flipped them over to give the other side an equal treatment.
The result was a tender juicy chicken leg with a nice crispy skin.