In a small bowl, mash together butter, chives, parsley and mustard with a fork until smooth. Cover with plastic wrap and let stand at cool room temperature while pork chops are cooking.
Preheat a gas grill on high, covered, for 10 minutes, and then lower heat to medium. Pat pork chops dry with paper towels and sprinkle generously with salt and pepper. Grill, turning once, until an instant-read thermometer inserted into center of meaty part of a chop (do not touch bone) registers 145°F, 12 to14 minutes total. Transfer chops to a platter and top each with 1 Tbsp. herb butter. Loosely tent with foil to keep warm, let stand 5 minutes and then serve hot.