01 - Remove the beef fillet from the refrigerator 30 minutes prior to cooking.
02 - Set the oven to 400°F (200°C).
03 - Pat the fillet dry with paper towels, rub all over with olive oil, then season generously with sea salt and black pepper.
04 - Heat an ovenproof skillet over high heat. Sear the beef fillet on all sides until browned, approximately 2 to 3 minutes per side.
05 - Add rosemary sprigs, unsalted butter, and crushed garlic to the skillet. Spoon melted butter over the fillet to enhance flavor.
06 - Transfer the skillet to the preheated oven and roast for 12 to 15 minutes for medium-rare (target internal temperature 125°F / 52°C) or until preferred doneness is achieved.
07 - Remove the fillet from the oven, transfer to a cutting board, and tent loosely with foil. Let rest for 10 minutes.
08 - Slice the fillet and sprinkle with chopped fresh parsley before serving.