Remove steaks from the refrigerator 45–60 minutes before cooking to bring to room temperature. This is not optional — it ensures even cooking.
Crush the peppercorns coarsely using a mortar and pestle, a spice grinder pulsed briefly, or by placing them in a zip-lock bag and crushing with a heavy skillet. You want cracked and coarsely ground pepper, not a fine powder.
Pat steaks completely dry with paper towels. Season all sides, including the edges, with kosher salt. Press the cracked peppercorns firmly onto both flat sides of each steak to form a crust. Let rest uncovered while you heat the pan.
Heat a heavy cast iron or stainless steel skillet over high heat until it is smoking hot — about 3–4 minutes. Add oil and let it shimmer.
Add steaks carefully. Do not move them. Sear 3–4 minutes until a deep mahogany crust forms. Flip once.
Add butter, smashed garlic, and thyme to the pan. As the butter melts and foams, tilt the pan slightly and use a spoon to continuously baste the steaks with the aromatic butter for 2–3 minutes.
Target internal temperatures: 125°F for rare, 130–135°F for medium-rare (recommended), 140°F for medium. Use an instant-read thermometer.
Transfer steaks to a cutting board and tent loosely with foil. Rest for at least 8–10 minutes. This step is critical — cutting too early loses all the juices.
For the pan sauce: Pour off most of the fat, leaving just a thin film. Over medium heat, sauté shallots 2 minutes. Add red wine and scrape up the browned bits, simmering until reduced by half. Add beef stock and reduce again by half. Remove from heat, whisk in butter and Dijon. Season with salt. Serve alongside or spooned over sliced steak.
Slice against the grain and serve immediately with the pan sauce, a simple green salad, and crusty bread to soak up the juices.