01 - Let the beef tenderloin steaks come to room temperature for 20 to 30 minutes. Pat dry with paper towels.
02 - Season steaks generously with kosher salt and black pepper on both sides.
03 - Heat the olive oil and 1 tablespoon butter in a large skillet over medium-high heat.
04 - When the pan is hot, add the steaks. Sear for 3 to 4 minutes per side for medium-rare, or adjust to desired doneness.
05 - Transfer steaks to a plate, tent loosely with foil, and let rest.
06 - Reduce heat to medium. In the same skillet, add green peppercorns and toast for 30 seconds.
07 - Deglaze the pan with white wine, scraping up any browned bits. Let it reduce by half, about 2 to 3 minutes.
08 - Add beef stock and simmer until slightly reduced, another 2 minutes.
09 - Lower the heat and stir in heavy cream and Dijon mustard. Simmer gently until thickened, 3 to 4 minutes.
10 - Stir in 1 tablespoon butter. Taste and adjust seasoning with salt if needed.
11 - Return the steaks to the pan to coat in the sauce, or spoon sauce generously over each steak to serve.