If chicken breasts are unevenly thick, place each between two pieces of plastic wrap and pound gently with a meat mallet or rolling pin to an even thickness about 0.75–1 inch thick. Pat dry with paper towels.

Make marinade

In a medium bowl combine 0.25 cups olive oil, 2 tbs lemon juice, 1 tbs soy sauce, 1 tsp Dijon mustard, 3 minced garlic cloves, 1 tbs honey, 1 tbs chopped rosemary, 1 tsp smoked paprika, 1.5 tsp kosher salt and 0.75 tsp black pepper. Whisk until emulsified.

Marinate

Place the 4 chicken breasts in a resealable plastic bag or shallow dish. Pour marinade over chicken, massaging to coat thoroughly. Seal or cover and refrigerate for at least 30 minutes and up to 4 hours (for best flavor, 2–4 hours). If short on time, allow at least 15–20 minutes at room temperature after removing from fridge before grilling.

Grilling

Preheat grill

Preheat your grill to medium-high heat (about 400–450°F / 200–230°C). If using a charcoal grill, set up for two-zone cooking with coals on one side for direct heat and an empty side for indirect. Oil the grates lightly using an oiled paper towel held with tongs.

Grill chicken

Remove chicken from marinade and let excess drip off. Place breasts over direct medium-high heat. Grill uncovered for 4–6 minutes on the first side without moving, until nice grill marks form. Flip and grill 4–6 minutes more. Internal temperature should reach 160–165°F (71–74°C) for juicy chicken; use an instant-read thermometer inserted into the thickest part. If breasts are thick and char before cooking through, move to indirect heat and close the lid for a few minutes until temperature reached.

Finish

Optional: during the final minute, add 1 tbs unsalted butter on top of each breast to melt and glaze. Remove chicken to a clean plate or cutting board and tent loosely with foil. Let rest 5–8 minutes so juices redistribute; carryover will bring temp to safe range.

Serve

Transfer chicken to serving platter. Sprinkle with 2 tbs chopped parsley if using and serve with lemon wedges alongside for squeezing. Slice across the grain to serve, or present whole. Adjust seasoning with extra salt and pepper to taste.