In a small saucepan combine onions, the water, and 1/4 teaspoon salt. Bring to boiling; reduce heat. Simmer, uncovered, for 3 minutes; drain. Cool slightly.
For relish, in a serving bowl whisk together vinegar, chipotle pepper, and 1/4 teaspoon salt. Stir in onions and blackberries. If desired, cover and chill for up to 24 hours. Let stand at room temperature for 1 hour before serving.
For a charcoal grill, place chops on the rack of an uncovered grill directly over medium coals. Grill about 5 minutes or until heated through, turning once halfway through grilling. (For a gas grill, preheat grill. Reduce heat to medium. Place chops on grill rack over heat. Cover and grill as above.)
To serve, stir the snipped parsley and the green onions into relish. Serve chops with relish. If desired, garnish with parsley sprigs.