The Sous Vide method is just as great for reheating steak as it is for cooking it. Start by placing your leftover steak in a sealable freezer bag with a small pat of salted butter. Squeeze out as much air as possible and allow the steak to come to room temperature, about 20-30 minutes. Once the refrigerator's chill is off the steak, the less time it will take for the beef to reheat.
Next, fill a large stockpot with water and attach a Sous Vide according to the machine's instructions. The water should be about 120°F to 130°F—warm enough for some steam to rise from the pot (note that the water should not reach a simmer). Place the airtight bag in the pot away from the edges and cook for about 5-8 minutes, or until the meat is gently warmed through. This gentle cooking method will keep your meat juicy, and prevent it from overcooking.
Set up for success:
Don't reheat your steak straight out of the fridge—have it sit out for about 30 minutes first. This will make it less likely for the steak to overcook and is an easy way to boost your chances of a successful reheating experience.
