Remove frozen steak from packaging and place in a ziploc bag, removing as much air as possible (I use frozen sealable bags). Fill sous vide machine with water and place steak in water.
Set sous to 129° for 1 hour and 20 minutes. Steak should be fully cooked at this point. Remove from bag, us a paper towel to dry steak on outside and season with pepper, salt, garlic, and rosemary etc.....
* To brown on outside * Turn skillet to medium-high heat and melt butter. Place steak in skillet and sear on both sides, 1-2 minutes per side basting with butter as it cooks.