Pat the steaks completely dry with paper towels. Season generously on all sides with kosher salt. Press the coarsely crushed peppercorns firmly onto both sides of each steak, creating an even crust.

Heat olive oil and butter in a large, heavy-bottomed skillet over medium-high heat. Once the butter is foaming, place the steaks in the pan. Sear for 3-5 minutes per side for medium-rare, or until a deep brown crust forms. Remove steaks from the pan and set aside to rest.

Reduce the skillet heat to medium. Add the minced shallot and cook for 1 minute until fragrant. Carefully pour in the Cognac to deglaze the pan, scraping up any browned bits from the bottom. Allow the alcohol to cook off for about 30 seconds.

Pour in the beef broth and simmer until it has reduced by half. Stir in the heavy cream and Dijon mustard. Continue to simmer for 2-3 minutes until the sauce thickens. Season with a pinch of salt if needed.

Return the steaks and any juices from the resting plate to the skillet. Spoon the sauce over the steaks. Serve immediately.