Preheat your oven to 375°F (190°C).
In a large bowl, combine the cooked chicken, spinach, and artichoke hearts.
In another bowl, mix sour cream, cream cheese, garlic powder, salt, and pepper until smooth.
Add the cheese mixture to the chicken and spinach mixture and stir to combine.
Transfer the mixture to a baking dish and top with mozzarella and parmesan cheese.
Bake for 45 minutes, or until the top is golden brown and bubbly.