The Real Reason You Should Sous Vide Your Steak
There's no worse feeling than buying an expensive cut of beef and then ruining it because of how you cooked it. While there is no foolproof method to cook a steak, there is a way that will make it significantly easier. That way is with a sous vide machine.
Putting the fancy French name (which means "under vacuum") aside, the method is a relatively simple one. All that is required is sealing your steak in a plastic bag and putting it in a sous vide machine, which heats water to a constant temperature and circulates it. If you are trying to cook your steak to medium rare, which would necessitate a 130 degree Fahrenheit internal temperature, you would want your water to be at 130 degrees (via Men's Journal). By the same token, if you want your steak to be cooked well-done (no judgement) your water should be slightly higher, and if you want it to be cooked rare, it should be slightly lower.
The benefits of using sous vide to cook steak
One benefit of cooking sous vide is that it's impossible to overcook your steak. Even if you leave it in there for hours, it will only cook to the temperature to which the water is heated. Also, since the steak is completely sealed, you are going to wind up with all of the flavors and juices locked in. One more upside? There's no need to let the meat rest after cooking, since according to Men's Health, the low and slow temperatures mean the "muscle fibers never seized."
However, sous vide machines won't sear meat so if you are a fan of a nice brown crust on your steak, you'll need to add a step at the end. You can always throw it in a skillet on high to create a crust, or you can even use a kitchen blowtorch. This method has a number of proponents such as chef J. Kenji López-Alt, a James Beard Award winner who has authored a number of cookbooks (via Anova Culinary). He calls sous vide "absolutely the better way" to cook a steak (via Serious Eats), so take it from the expert and give this method a try.