01 - In a mixing bowl, whisk together maple syrup, apple cider vinegar, soy sauce or tamari, Dijon mustard, minced garlic, smoked paprika, salt, and black pepper until thoroughly combined.
02 - Place chicken thigh pieces in a resealable bag or shallow dish. Pour half of the glaze over the chicken, ensure even coating, and refrigerate for a minimum of 15 minutes up to 1 hour. Set aside the remaining glaze for basting.
03 - Thread marinated chicken, apple wedges, and red onion pieces alternately onto skewers, leaving a small gap between each for even cooking.
04 - Heat the grill to medium-high, approximately 400°F. Oil the grates lightly to prevent food from sticking.
05 - Position assembled skewers on the grill. Cook for 6 minutes, brush with reserved glaze, and turn. Continue grilling for an additional 6 minutes, basting once more, until chicken is fully cooked and apples are lightly charred.
06 - Transfer grilled skewers to a platter and allow to rest for 3 minutes before serving warm. Optionally, garnish with freshly chopped parsley.