Preheat your oven to 350°F (175°C) and generously grease a 9x13-inch baking dish with cooking spray or butter.

Cook the spaghetti according to package directions until al dente, drain well, and set aside. Reserve 1 cup of pasta cooking water in case needed later.

In a large skillet, heat olive oil over medium heat. Add diced onion, bell pepper, and celery, cooking for 5-7 minutes until vegetables are softened and onions are translucent.

Add minced garlic and cook for an additional minute until fragrant. Remove from heat and set aside.

In a large mixing bowl, combine both cream soups, chicken broth, softened cream cheese, and all spice blend ingredients. Whisk until smooth and well combined.

Add the cooked vegetables, diced chicken, and cooked spaghetti to the soup mixture. Toss everything together until well coated.

Fold in 1½ cups of the cheddar cheese and ¾ cup of the Monterey Jack cheese, reserving the remaining cheese for topping.

Transfer the mixture to your prepared baking dish, spreading it evenly. Top with remaining cheeses.

In a small bowl, combine breadcrumbs with melted butter and sprinkle over the top of the casserole.

Cover with aluminum foil and bake for 30 minutes. Remove foil and continue baking for 15-20 minutes until bubbly and golden brown on top.

Let the casserole rest for 10 minutes before serving. Garnish with fresh parsley and green onions.

Serve hot and enjoy this Southern comfort food masterpiece with your favorite sides.