Prepare the Casserole

1. Preheat Oven: Preheat your oven to 375°F (190°C). Grease a 9×13-inch baking dish.
2. Prepare the Sauce: In a large mixing bowl, combine the sour cream, mayonnaise, 1/2 cup of Parmesan cheese, mozzarella cheese, garlic powder, onion powder, salt, and pepper. Stir until well combined.
3. Add Chicken: Fold the cubed chicken into the sauce, ensuring each piece is coated evenly.
4. Transfer to Baking Dish: Spread the chicken mixture evenly in the prepared baking dish.

Add the Topping

1. Prepare the Topping: In a small bowl, mix the Panko breadcrumbs, melted butter, and remaining 1/2 cup of Parmesan cheese until well combined.
2. Sprinkle the Topping: Evenly sprinkle the breadcrumb mixture over the top of the casserole.

Bake

1. Bake in the Oven: Place the casserole in the preheated oven and bake for 30-40 minutes, or until the top is golden brown and the chicken is cooked through.
2. Cool Slightly: Allow the casserole to cool for a few minutes before serving.