Instructions

1. If time allows, season both sides of steak with kosher salt Allow to sit, refrigerated, 6-12 hours. (The salt breaks down the cell structure tenderizing the meat.)
2. Let the meat come to room temperature then season both sides with freshly ground pepper.
3. Whisk together beef stock, Dijon and Worcestershire and reserve.
4. Heat 1 tablespoon butter and oil in a large to medium high heat, or until oil is hot but not smoking. Sear steaks about 3 minutes on each side, or until golden browned on each side.* Remove steaks from heat, place on plate and lightly tent with foil.
5. Remove pan from heat and add shallots and garlic to pan juices, stirring. Residual heat from pan will be hot enough to cook them. Stir until golden brown and wilted, about 2 minutes.
6. Return pan to a medium-high heat, and immediately stir in mushrooms and remaining tablespoon butter. Cook 1-2 minutes or until mushrooms are just beginning to become limp.
7. Raise heat to high and add brandy or cognac. Reduce 20 seconds then whisk in beef stock, Dijon and mustard mustard. Reduce on high heat 3-4 minutes, stirring, or until sauce is velvety smooth and thickened. Stir in cream. (If steaks need additional cooking, they may reheat in sauce at this time.) Serve steaks with sauce, garnished with chives.
8. If you prefer your steaks medium to well-done; place them in a warm oven (200 degrees) to continue cooking as you make your sauce.