|Sprinkle steaks with salt and pepper. Heat oil in a 9-inch cast-iron skillet over medium-high heat. Add staks and cook 5 minutes on each side, or until desired degree of doneness. Remove steaks from pan and keep warm. Add shallots to pan and saute for 30 seconds. Add cognac and cook for another 10 seconds. Add broth and mustard while stirring thoroughly. Reduce heat and cook for 2 minutes, stirring constantly. Serve steaks with sauce.