Follow these steps to create your Chicken Cordon Bleu Casserole effortlessly:

1. Preheat Oven: Preheat your oven to 350°F (175°C).
2. Prepare Baking Dish: Grease a 9×13-inch casserole dish with cooking spray or butter.
3. Combine Ingredients: In a large mixing bowl, combine the diced chicken, sliced ham, cooked rice, Swiss cheese, and cheddar cheese.
4. Mix the Sauce: In a separate bowl, whisk together the cream of chicken soup, milk, garlic powder, onion powder, black pepper, and Dijon mustard until smooth.
5. Combine Everything: Pour the sauce over the chicken and cheese mixture. Stir until everything is evenly coated.
6. Transfer to Dish: Pour the combined mixture into the prepared casserole dish. Spread it evenly.
7. Prepare Topping: In a small bowl, mix breadcrumbs with melted butter. Sprinkle this mixture evenly over the casserole.
8. Bake: Place in the oven and bake uncovered for 30-35 minutes, or until bubbly and the topping is golden brown.
9. Garnish: Remove from the oven and let it sit for a few minutes. Garnish with freshly chopped parsley if desired.

These steps will guide you in creating an incredible Chicken Cordon Bleu Casserole that is sure to impress everyone at the table.