Heat slow cooker on low setting.
To the slow cooker, add chicken, chicken stock, buffalo wing sauce, green onion, carrots, celery, and garlic. Cover and cook 6 hours.
Add cheddar, parmesan and blue cheeses. Stir until cheeses are melted and mixed in. Cover and cook 1 additional hour.
Garnish with blue cheese crumbles and parsley before serving.