Remove the 10 oz filet mignon from the refrigerator and pat dry with paper towels. Let sit at room temperature for 30–45 minutes to take the chill off (this promotes even cooking). Just before cooking, press 1 tablespoon kosher salt and 1 teaspoon freshly ground black pepper evenly onto all sides of the steak.

Preheat pan and oil

Place a heavy skillet (cast iron preferred) over medium-high to high heat and heat until shimmering and very hot, about 4–5 minutes. Add 1 teaspoon neutral oil and swirl to coat the pan; it should immediately shimmer and barely smoke.

Sear the steak

Place the filet in the hot pan and leave undisturbed for 2.5–3 minutes to develop a deep brown crust. Using tongs, rotate the steak to sear the sides for about 20–30 seconds each to render any outer fat and create color. Flip the steak and sear the other flat side for 2.5–3 minutes for a medium-rare finish (internal temperature about 125–130°F / 52–54°C). Adjust searing times by 30–60 seconds per side for rarer or more well-done results.

Finishing & Basting

Add butter and aromatics

When the second side is nearly done, reduce heat to medium. Add 2 tablespoons unsalted butter, the 2 crushed garlic cloves, 2 thyme sprigs and 1 rosemary sprig (if using) to the pan beside the steak.

Baste the steak

Tip the pan slightly so the melted butter pools. Using a large spoon, continuously baste the steak with the melted butter and pan juices for 1–2 minutes, spooning over the top to build flavor and encourage even finish. Continue until the steak reaches your target internal temperature (about 125–130°F / 52–54°C for medium-rare).

Optional oven finish (if steak is very thick)

If the filet is thicker than 1.75–2 inches or you prefer a gentler finish, after searing both sides transfer the hot skillet to a 400°F (200°C) oven for 4–6 minutes while basting once, then remove when desired internal temperature is reached.

Resting & Serving

Rest the steak

Transfer the filet to a warm plate or cutting board and tent loosely with foil. Let rest undisturbed for 5–8 minutes; this lets juices redistribute and the carryover will bring the steak to final doneness.

Finish and serve

After resting, sprinkle about 1/4 teaspoon coarse sea salt and 1/4 teaspoon freshly ground black pepper over the steak. Slice or serve whole. Spoon any butter and pan juices over the steak when plating. Serve immediately.