Preheat your oven to 375°F (190°C).

In a large bowl, combine your cooked chicken, chopped artichoke hearts, and frozen spinach. Stir until mixed.

Add mayonnaise, sour cream, mozzarella cheese, Parmesan cheese, garlic powder, onion powder, black pepper, and salt to the mixture. Stir until well combined.

Grease your 9x13-inch baking dish with olive oil.

Evenly spread the creamy chicken-spinach mixture into the greased baking dish.

In a separate bowl, combine breadcrumbs with melted butter. Mix thoroughly.

Sprinkle the breadcrumb mixture evenly over the casserole. Add remaining mozzarella and Parmesan cheese on top.

Cover the dish with foil and bake for 20 minutes.

After 20 minutes, remove the foil and bake uncovered for another 10-15 minutes until bubbly and golden.

Let the casserole cool for 5-10 minutes before serving.