Remove the tenderloin steaks from the refrigerator 30–40 minutes before cooking so they come to near room temperature. Pat them dry with paper towels.

Season both sides of each steak evenly with kosher salt (about 1/2 tsp per side depending on thickness) and freshly ground black pepper.

Preheat a heavy skillet (cast iron preferred) over medium-high heat until very hot, about 5 minutes. Alternatively preheat a grill to high direct heat.

Add 2 tbs olive oil to the skillet and swirl to coat. Place steaks in the hot pan without crowding. Sear steaks for 3–4 minutes on the first side until a deep brown crust forms.

Flip steaks, add 2 tbs unsalted butter and the thyme sprigs to the pan. As the butter melts, tilt the pan and spoon butter over the steaks (baste) for another 3–4 minutes for medium-rare (internal temp 54–57°C / 130–135°F). Adjust time ±1–2 minutes for desired doneness.

Transfer steaks to a warm plate or cutting board and tent loosely with foil. Rest steaks for 6–8 minutes to allow juices to redistribute while you make the sauce.

Sauce au Poivre (Peppercorn Sauce)

While steaks are resting, use the same skillet with the fond (brown bits) left in it. If there's an excessive amount of fat in the pan (more than ~1 tbs), carefully pour off all but about 1 tbs.

Over medium heat add the minced shallot to the skillet and sauté for 1–2 minutes until softened and translucent, scraping up any browned bits with a wooden spoon.

Add the crushed green and black peppercorns and cook, stirring, for about 30 seconds to bloom the pepper aromatics.

Carefully add the brandy or cognac (stand back slightly). If you are comfortable, flambé to burn off the alcohol by tipping the pan or ignite with a long lighter. If you do not want to flambé, allow the alcohol to simmer and reduce for 1 minute to cook off most of the alcohol.

Add the beef stock and bring to a simmer. Reduce the liquid by about half, simmering for 4–6 minutes, until slightly thickened and reduced to roughly 120–150 ml.

Lower the heat to medium-low and stir in the heavy cream and Dijon mustard. Simmer gently for 2–3 minutes until the sauce thickens slightly and coats the back of a spoon.

Whisk in the cold cubed butter a few pieces at a time to emulsify and give the sauce a silky sheen. Taste and season with up to 1 tsp salt, adjusting to your preference.

If the sauce is too thick, thin with a splash (1–2 tbs) of warm beef stock or water. Keep warm over very low heat but do not boil after adding cream.

Finish & Serve

Slice steaks if desired or serve whole. Spoon the warm peppercorn sauce over each steak or serve the sauce on the side in a small sauceboat.

Garnish with a thyme sprig and finish with a small pinch of coarse sea salt if desired. Serve immediately.