Preheat the oven to 180°C (350°F).
In a large mixing bowl, combine sour cream, cream cheese, and mayonnaise until smooth.
Add shredded chicken, garlic powder, salt, and black pepper and mix well.
Stir in cheddar cheese and mozzarella cheese until evenly combined.
Spread the mixture evenly into a greased baking dish.
In a small bowl, mix crushed crackers with melted butter.
Sprinkle the cracker topping evenly over the casserole.
Bake in the preheated oven for 30 minutes until bubbly and golden.
Remove from oven and let rest for 5 minutes.
Garnish with fresh parsley and serve warm.