Sprinkle steaks with pepper and salt. In a large skillet, heat 2 tablespoons butter over medium heat. Add green onion and mustard; cook 1 minute. Add steaks; cook 2-5 minutes on each side or until meat reaches desired doneness (for medium-rare, a thermometer should read 135°; medium 140°; medium-well, 145°)., Remove steaks to a serving platter and keep warm. In same skillet, add lemon juice, Worcestershire sauce and remaining butter; cook and stir 2 minutes or until thickened. Add parsley and chives. Serve with steaks.