Melt butter in microwave or on stovetop. Stir in honey, Dijon mustard, olive oil, and lemon juice. Season with salt and pepper to taste.
Transfer about half of the honey mustard mixture to a separate bowl for later.
Preheat grill to 425 degrees F, medium heat.
Pound thicker parts of chicken breasts for more even thickness, about 1 inch thick. Season both sides chicken with salt and pepper.
Brush grill grates lightly with oil. Grill chicken for 4 minutes, then brush with honey mustard glaze, and flip chicken to cook other side. Brush the other side with glaze and cook for another 4-5 minutes, or until done. (Internal temperature of the thickest part of chicken should reach 165 degrees when done.) Transfer chicken to a plate or platter.
Use reserved glaze to brush both sides of chicken and let rest a few minutes before serving. Garnish with fresh parsley, if desired.
Air Fryer Instructions
Melt butter in microwave or on stovetop. Stir in honey, Dijon mustard, olive oil, and lemon juice. Season with salt and pepper to taste.
Transfer about half of the honey mustard mixture to a separate bowl for later.
Pound down the chicken for a more even thickness, about 1 inch thick.
Brush both sides of the chicken with honey mustard glaze and then place inside the air fryer basket.
Cook at 380F/190C for 11-12 minutes, flipping at the halfway point.
For the best results: All air fryers are different, as well as the size of your chicken, because of this check on the chicken every 3-4 minutes of cooking and adjust as needed. Pull the chicken out once it reaches about 160F/71C and tent it in tinfoil to finish cooking and reaches an internal temp of 165F/74C.