01 - Place chicken thighs in the bottom of the slow cooker in a single even layer.
02 - In a medium bowl, whisk together basil pesto, ranch seasoning mix, chicken broth, heavy cream, and grated Parmesan cheese until thoroughly combined and smooth.
03 - Pour the sauce mixture evenly over the chicken thighs, ensuring all pieces are covered.
04 - Cover and cook on LOW setting for 4 to 6 hours, or until chicken reaches internal temperature of 165°F and is tender throughout.
05 - Transfer chicken to a serving platter, spoon sauce generously over the top, and garnish with chopped fresh basil and additional grated Parmesan cheese.