Remove filets from the fridge 30–45 minutes before cooking to bring to room temperature. Pat dry with paper towels and generously season both sides with kosher salt and a light dusting of freshly ground black pepper.

Heat a cast-iron skillet over medium-high heat. Add olive oil and let it shimmer but not smoke.

Add steaks and sear, without moving, for 3–4 minutes until a deep golden crust forms. Flip and add butter, crushed garlic, and thyme. Spoon the melted butter over the steaks for about 1–2 minutes.

Transfer the skillet to the preheated oven. Roast for 4–7 minutes depending on thickness and desired doneness: aim for 120–125°F for rare, 125–130°F for medium-rare, and 135°F for medium. (The steaks will rise ~5°F while resting.)

Remove steaks to a cutting board, tent loosely with foil, and rest for 7–10 minutes to keep the meat tender.

Return the skillet to medium heat (careful — handle will be hot). Remove excess fat, leaving about 1 tablespoon in the pan.

Add 2 tablespoons butter and the chopped shallot. Sauté 1–2 minutes until translucent and fragrant.

Stir in crushed black peppercorns and cook for 30 seconds. If using brandy, carefully add it now to deglaze the pan — tilt the pan slightly so the alcohol burns off, or simmer for 1–2 minutes to reduce.

Pour in beef broth and simmer for 2–3 minutes until slightly reduced.

Lower heat to medium-low and stir in heavy cream and Dijon mustard. Simmer gently for 3–4 minutes until the sauce thickens to coat the back of a spoon. Taste and add salt if needed. Fold in green peppercorns if using.

Finish the sauce with a pat of butter for shine and extra richness. Spoon over rested filets and garnish with parsley.