01 - Place the sliced onion and minced garlic in the bottom of the slow cooker, creating an even layer to rest the chicken on.
02 - Arrange the chicken thighs in a single layer over the onion and garlic, ensuring even cooking.
03 - In a small bowl, whisk together the balsamic vinegar, honey, chicken broth, Dijon mustard, olive oil, basil, oregano, salt, and black pepper until fully combined.
04 - Pour the sauce evenly over the chicken thighs, coating all pieces.
05 - Cover and cook on low for 6 hours or on high for 4 hours, until the chicken is tender and reaches an internal temperature of 165°F.
06 - Remove the chicken and set aside. Pour the sauce into a saucepan and simmer for 5–8 minutes to thicken, then return the chicken to the sauce.
07 - Garnish with fresh parsley before serving over rice, mashed potatoes, or steamed vegetables.