Preheat your oven to 375°F and prepare a 9x13 inch baking dish by coating it lightly with cooking spray to prevent sticking.

Bring a large pot of salted water to a rolling boil and cook the elbow macaroni according to package directions until al dente, usually about 7-8 minutes, then drain thoroughly and set aside.

In a large saucepan over medium heat, melt the butter completely until it begins to foam, then sprinkle in the flour and whisk continuously for about 2 minutes until the mixture becomes lightly golden and fragrant.

Gradually pour in the milk or cream while whisking constantly to prevent lumps, continuing to cook and stir until the sauce thickens enough to coat the back of a spoon, approximately 5-7 minutes.

Remove the saucepan from heat and add the shredded cheddar and Monterey Jack cheeses, stirring until completely melted and the sauce is smooth and creamy.

Season the cheese sauce with garlic powder, onion powder, smoked paprika, salt, and black pepper, stirring well to distribute the seasonings evenly throughout.

In a large mixing bowl, combine the cooked macaroni, shredded chicken, and three-quarters cup of BBQ sauce, tossing everything together until evenly distributed.

Pour the creamy cheese sauce over the macaroni and chicken mixture, folding everything together gently but thoroughly until every piece is coated in that luscious sauce.

Transfer the entire mixture into your prepared baking dish, spreading it out evenly and pressing down lightly to eliminate any air pockets.

Drizzle the remaining quarter cup of BBQ sauce over the top surface, using a spoon or brush to spread it into an even layer that will caramelize beautifully during baking.

Place the baking dish in the preheated oven and bake for 25-30 minutes until the top is golden brown, bubbling around the edges, and slightly caramelized from the BBQ sauce.

Remove from the oven and let the casserole rest for 5-10 minutes before serving, allowing the cheese sauce to set slightly for easier serving, then garnish with freshly chopped parsley.