01 - Place the sliced red onion and minced garlic evenly across the bottom of the slow cooker insert.
02 - Lay the chicken thighs in a single layer on top of the onion and garlic, ensuring even distribution.
03 - In a small mixing bowl, whisk together the balsamic vinegar, honey, chicken broth, Dijon mustard, olive oil, dried basil, dried oregano, salt, and black pepper until fully combined.
04 - Pour the prepared balsamic mixture evenly over the chicken thighs, coating all pieces.
05 - Cover and cook on low setting for 6 hours or on high setting for 4 hours, until the chicken reaches an internal temperature of 165°F and is tender.
06 - For a thicker sauce, remove the cooked chicken and set aside. Transfer the liquid to a saucepan and simmer over medium heat for 5-8 minutes until reduced. Return the chicken to the sauce before serving.
07 - Sprinkle with chopped fresh parsley just before serving.