Combine the potatoes, olive oil, 3/4 teaspoon of salt, 1/2 teaspoon of black pepper, and paprika in the bottom of a slow cooker. Stir everything until the potatoes are well coated.
Place the chicken pieces on top of the potatoes and sprinkle with the remaining salt and pepper.
In a separate bowl, whisk together the Parmesan garlic sauce and water until well combined. Pour this mixture over the chicken and potatoes.
Cook on High for 4 hours or on Low for 6 hours, until the chicken is cooked through and the potatoes are tender.
During the last 20 minutes of cooking, add the mozzarella and Parmesan cheese. Continue to cook, covered, until the cheese is melted.
Sprinkle with chopped parsley before serving.