1. Prepare the Chicken: Pat the boneless, skinless chicken breasts dry with paper towels. If very thick, pound them lightly to an even 1-inch thickness.

2. Whisk the Marinade: In a medium bowl, combine the BBQ sauce, honey, Dijon mustard, olive oil, garlic powder, onion powder, and black pepper. Whisk until smooth and well combined.

3. Marinate the Chicken: Place the patted-dry chicken breasts into the bowl with the marinade, or put them in a large zip-top bag. Ensure each piece of chicken is fully coated. Marinate at room temperature for at least 15-20 minutes, or refrigerate for up to 4 hours.

4. Preheat the Grill: While the chicken is marinating, preheat your outdoor grill to medium-high heat (about 400-425 F). Lightly oil the grill grates to prevent sticking.

5. Grill the Chicken: Carefully place the marinated chicken breasts on the hot, oiled grill grates. Discard any remaining marinade. Grill for 6-8 minutes per side, or until the internal temperature reaches 165 F when measured with an instant-read meat thermometer inserted into the thickest part of the chicken.

6. Rest and Serve: Remove the chicken from the grill and transfer it to a clean cutting board or plate. Tent it loosely with aluminum foil and let it rest for 5-10 minutes. Slice and serve warm, garnished with fresh parsley or chives if desired.