Preheat water bath to 130°F or 54°C for medium rare, vacuum seal steak.
Place steak in bath for 1 hour for a 1 inch thick steak, I used a t-bone.
After 30 sec.-1min, flip your steak. After another 30 sec-1 min, remove the steak from the pan and let it rest. Keep the pan on the flame, reduce heat, and add some butter butter and a few stalks of rosemary. Cook until the butter is brown and the rosemary is crystallized, then pour from the pan into a bowl.
Once your steak is rested, plate it and serve the butter on the side. Its better to dip the steak in the butter or spoon the butter on the side of the plate than to pour it over the steak itself, as the caramellized flavour of the butter will diminish after sitting on the steak for a while. The crystallized rosemary can, however, be placed directly on the steak.