Remove the 6 oz A5 Wagyu filet from refrigeration 45–60 minutes before cooking and keep wrapped loosely on a tray in a cool area. The goal is to take the interior nearer to room temperature for even cooking—do not leave out more than 60 minutes.

Pat dry and season

Pat the steak thoroughly dry with paper towels. Lightly score any excess exterior fat edge once or twice (do not cut into the meat). Season both sides very lightly with kosher salt (about 1 tsp total) and a light dusting of freshly ground black pepper (about 1/2 tsp). Because A5 Wagyu is extremely rich, use a restrained amount of seasoning.

Preheat pan

Select a heavy cast-iron or stainless steel skillet and heat it over medium-high heat until shimmering and very hot, about 4–6 minutes. Add 1 tablespoon neutral oil and swirl to coat. The pan should be hot enough that the oil moves fluidly and just begins to smoke.

Sear the filet

Place the filet in the hot pan and press gently to ensure full contact. Sear undisturbed for 45–60 seconds to develop a caramelized crust. Turn the filet and sear the second long side for another 45–60 seconds. Sear the fat cap or edge for 15–30 seconds, allowing some of the rendered fat to baste the meat.

Finish with butter and aromatics

Reduce heat to medium-low, add 1 tablespoon unsalted butter, the thyme sprig and the lightly crushed garlic clove (if using) to the pan. As the butter melts, tilt the pan slightly and use a spoon to baste the steak continuously for 30–60 seconds. Baste until the exterior registers about 115–118°F (46–48°C) for rare; A5 is best served rare to medium-rare to preserve its buttery texture.

Rest

Transfer the filet to a warm plate or cutting board and tent loosely with foil. Rest for 5–7 minutes to allow juices to redistribute. During resting, the internal temperature will rise about 5–7°F.

Finish and slice

After resting, if serving whole, top with a pinch (about 1/4 tsp) of flaky sea salt. Alternatively, slice the filet into 3–4 medallions with a very sharp knife and lightly sprinkle flaky sea salt across the exposed surfaces.

To serve (optional)

Plate the steak over a small bed of microgreens or baby arugula if desired. Offer a small amount of grated horseradish or wasabi and a teaspoon of ponzu or soy sauce on the side for those who prefer a contrasting acid or heat. Serve immediately.