01 - Layer sliced red onion and minced garlic evenly across bottom of slow cooker insert.
02 - Place chicken thighs in single layer atop onion and garlic bed.
03 - Whisk balsamic vinegar, honey, chicken broth, Dijon mustard, olive oil, basil, oregano, salt, and pepper in small bowl until fully incorporated.
04 - Pour sauce mixture evenly over chicken thighs ensuring all pieces are coated.
05 - Cover and cook on low setting 6 hours or high setting 4 hours until chicken reaches internal temperature 165°F and tender.
06 - Transfer chicken to platter. Pour cooking liquid into saucepan and simmer 5-8 minutes until reduced and thickened. Return chicken to sauce.
07 - Sprinkle fresh parsley over chicken before serving.