1. Preheat your outdoor grill to medium-high heat (around 400 F / 200 C). While the grill is heating, lightly oil the grates to prevent sticking. A paper towel dipped in a little vegetable oil and held with tongs works well for this.

2. In a medium bowl, combine the melted unsalted butter, minced garlic, chopped fresh parsley, lemon juice, salt, and black pepper. Whisk everything together until well combined. The sauce should be fragrant and slightly emulsified.

3. Pat the boneless, skinless chicken thighs dry with paper towels. This step is important for achieving a good sear and preventing the chicken from steaming. Place the chicken in a shallow dish or on a baking sheet.

4. Brush a generous amount of the garlic butter sauce over both sides of each chicken thigh. Make sure they are evenly coated, reserving about a quarter of the sauce for basting during grilling.

5. Place the seasoned chicken thighs on the preheated, oiled grill grates. Close the lid and cook for 6-8 minutes per side. You’re looking for nice grill marks and for the chicken to be cooked through.

6. During the last few minutes of cooking, brush the chicken with the reserved garlic butter sauce. Continue to grill until the internal temperature of the thickest part of the chicken reaches 165 F (74 C) using an instant-read meat thermometer. The chicken should be golden brown and the juices should run clear.

7. Once cooked, remove the chicken thighs from the grill and let them rest on a cutting board or platter for 5 minutes before serving. This allows the juices to redistribute, ensuring the chicken stays tender and moist.