Wash chicken and pat dry. Brush with butter. Sprinkle with salt and pepper. Place in crock pot. Sprinkle with dry salad mix. Cover and cook on low for 5 to 6 hours. About 3/4 hour before serving, mix soup, cream cheese, wine, and onion in small saucepan. Cook until smooth. Pour over chicken in pot. Cover and cook for 30 minutes on low. Serve with sauce.