01 - In a medium bowl, whisk together the maple syrup, Dijon mustard, olive oil, apple cider vinegar, minced garlic, thyme, salt, and black pepper until the mixture is fully emulsified.
02 - Place the chicken breasts in a large resealable bag or a shallow dish. Pour the marinade over the chicken, ensuring each piece is evenly coated. Seal the container and refrigerate for at least 1 hour, or up to 8 hours for deeper flavor penetration.
03 - Preheat your grill to medium-high heat. Lightly oil the grill grates to prevent sticking.
04 - Remove the chicken from the marinade, shaking off any excess liquid. Discard the used marinade.
05 - Grill the chicken breasts for 5 to 7 minutes on each side, or until the meat is fully cooked and the internal temperature reaches 165°F.
06 - Transfer the chicken to a cutting board and let it rest for 5 minutes before slicing. Garnish with fresh parsley and serve with lemon wedges if desired.