If the breasts are very thick, butterfly each one or pound to an even thickness about 1/2 to 3/4 inch using a meat mallet or rolling pin between sheets of plastic wrap. Pat the chicken dry with paper towels.

Make the marinade

In a medium bowl, whisk together 1 tablespoon olive oil, 2 tablespoons lemon juice, minced garlic, 1 tablespoon Dijon mustard, 1 teaspoon honey, 1 teaspoon smoked paprika, 1 teaspoon dried oregano, 1 1/2 teaspoons kosher salt, and 3/4 teaspoon freshly ground black pepper until smooth and uniform.

Marinate

Place the chicken breasts in a shallow dish or zip-top bag. Pour the marinade over the chicken, turning to coat thoroughly. Arrange the breasts in a single layer. Cover and refrigerate for at least 30 minutes and up to 4 hours. If short on time, let rest 15 minutes at room temperature after coating.

Preheat the grill

Preheat a gas or charcoal grill to medium-high heat, about 400–450°F (200–230°C). Clean and oil the grates: use a folded paper towel dipped in oil and tongs to rub the grates to prevent sticking.

Grill the chicken

Remove chicken from the fridge 10–15 minutes before cooking to take the chill off. Place the breasts on the grill over direct heat. Grill, uncovered, 5–7 minutes per side, turning once, until an instant-read thermometer inserted into the thickest part reads 165°F (74°C). Cooking time will vary based on thickness; thinner pieces will take less time. Do not press down on the chicken while grilling to retain juices.

Finishing & Optional Garnish

Rest and finish

When the internal temperature reaches 165°F, transfer the chicken to a clean platter. Immediately add 1 tablespoon unsalted butter on top of the hot breasts to melt and baste for extra richness. Tent loosely with foil and let rest 5 minutes to allow juices to redistribute.

Garnish and serve

Sprinkle the chopped fresh parsley over the chicken and serve with lemon wedges on the side for squeezing. Taste and add additional salt or pepper if needed.