Combine potatoes, olive oil, ¾ teaspoons salt, ½ teaspoon black pepper, and paprika in the bottom of a slow cooker and stir until well coated.
Add chicken pieces on top and sprinkle with remaining salt and pepper.
Whisk Parmesan garlic sauce and water together in a bowl until well incorporated.
Pour mixture over chicken and potatoes.
Cook on High for 4 hours (or on Low for 6 hours), or until chicken is cooked through and potatoes are tender.
During the last 20 minutes of cooking, add mozzarella and Parmesan and continue to cook, covered.
Sprinkle with parsley to serve.
