Divide beef into 2 steaks. Season steaks with pepper. Cook steaks in hot butter, 2 mins on each side, or more depending on desired doneness. Season with salt. Remove steaks to a warm plate. Add 1T. butter to pan. Add shallots and mushrooms and cook until all liquid has evaporated. Deglaze pan with vodka. Cook 1 min. Stir in mustard cook 1 min. Stir in cream. Check seasonings. Quickly reheat steaks. Serve with rosti potatoes or rice.