Remove the filet mignon steaks from the Refrigerator 30–45 minutes before cooking and let them come to room temperature. This ensures even cooking throughout. Pat both steaks completely dry with paper towels — this is the key to a great sear. Season generously on all sides (top, bottom, and edges) with 1 tsp kosher salt and freshly ground ½ tsp black pepper, 现磨.

Preheat your Oven to 400°F. Place a Cast Iron Skillet over high heat and let it heat for 2–3 minutes until it is very hot and just beginning to smoke. Add the vegetable oil and swirl to coat.

Carefully place the steaks in the Cast Iron Skillet. Do not move them. Sear for 2–3 minutes until a deep, dark-brown crust forms on the bottom. Flip the steaks and sear the other side for another 2 minutes.

Reduce the heat to medium. Add the 2 tbsp unsalted butter, smashed 3 cloves of garlic cloves, and 3 pieces of thyme, 新鲜 to the Cast Iron Skillet. Once the 2 tbsp unsalted butter melts and foams, tilt the pan slightly and use a Wooden Spoon to continuously baste the tops of the steaks with the herb 2 tbsp unsalted butter for about 1 minute.

Transfer the Cast Iron Skillet to the preheated Oven. Roast until the steaks reach your desired internal temperature: 125°F for rare, 130–135°F for medium-rare, 140°F for medium. For 1.5-inch thick steaks, medium-rare typically takes 6–8 minutes. Use an Meat Thermometer for accuracy.

Transfer the steaks to a Cutting Board or warm plate and tent loosely with Aluminum Foil. Let them rest for at least 5–7 minutes — this allows the juices to redistribute and is non-negotiable for a juicy steak. Reserve the Cast Iron Skillet with all drippings for the sauce.

Carefully pour off all but about 1 teaspoon of the drippings from the Cast Iron Skillet, leaving behind the fond (the browned bits on the bottom). Discard the 3 cloves of garlic and 3 pieces of thyme, 新鲜 from the steak. Place the Cast Iron Skillet over medium heat and add 1 tablespoon of 2 tbsp unsalted butter.

Add the minced 1 shallot, 细碎 and cook, stirring, for 1–2 minutes until softened and translucent. Add the minced 3 cloves of garlic and cook for 30 seconds more until fragrant.

Pour in the red wine and increase the heat to medium-high. Use a Wooden Spoon to scrape up all the browned bits from the bottom of the pan — this is where all the flavor lives. Bring to a boil and let the wine reduce by about half, approximately 4–5 minutes.

Add the 1 cup beef stock and fresh 3 pieces of thyme, 新鲜. If using, Whisk in the 1 tsp dijon mustard. Continue to simmer over medium-high heat, stirring occasionally, until the sauce has reduced by about half and is thick enough to coat the back of a spoon, about 6–8 minutes.

Remove the Cast Iron Skillet from the heat. Add the cold 2 tbsp unsalted butter cubes one at a time, swirling the pan or whisking constantly after each addition until fully melted and incorporated. This technique (called 'mounting') gives the sauce a glossy, restaurant-quality finish. Season to taste with 1 tsp kosher salt and ½ tsp black pepper, 现磨.

Place each rested filet mignon on a warm plate. Spoon the red wine sauce generously around and over the steaks. Garnish with freshly chopped 1 tbsp parsley, 细切，新鲜 (optional) if desired. Serve immediately.