Special Equipment: Sous-Vide Cooker (or BBQ)
Set Sous-Vide cooker to 130°F (54.4°C). If not using a Sous-Vide, see below.
Generously season steaks with salt and pepper. Place 2 Tbsp oil, shallots, rosemary, and garlic (if using) into resealable or vacuum-seal bags. Place steaks in bags and seal.
Following operating instructions for your Sous-Vide cooker, place bag(s) in water bath and set timer for 2 hours.
After 2 hours, remove steaks from bags and dry well with paper towels.
Heat large cast iron skillet or grill pan over high heat. Rub dried steaks with remaining Tbsp of oil. Add steaks to hot pan and sear until well browned, about 30 seconds per side. Transfer steak to cutting board and let rest for 5 minutes. Serve.
Make this recipe without a Sous-Vide cooker:
follow directions to marinate steaks in a sealable bag for 2 hours. After 2 hours, remove the steaks and prepare your grill. Grill to desired doneness.