Press each tenderloin piece into 1 inch thick medallion; sprinkle surfaces with lemon pepper.
Melt butter in large heavy skillet over medium heat. Add medallions; cook 3 to 4 minutes on each side. Remove pork to serving platter; keep warm.
Stir lemon juice, worcestershire sauce and mustard into pan juices in skillet. Cook, stirring, until heated through. Pour sauce over medallions; sprinkle with chopped chives.