Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish or lightly spray it with non-stick cooking spray.

Cook Macaroni: In a large pot of boiling salted water, cook the elbow macaroni according to package instructions until al dente. Drain and set aside.

Prepare Cheese Sauce: In a medium saucepan, melt the butter over medium heat. Add the garlic powder, onion powder, and paprika, and stir for about 30 seconds until fragrant. Add the cream of chicken soup, milk, and sour cream. Stir until well combined and heated through. Gradually add the shredded cheddar and mozzarella cheeses, stirring constantly until the cheese is melted and the sauce is smooth.

Combine Ingredients: In a large bowl, combine the cooked macaroni, diced chicken, and cheese sauce. Mix until everything is well coated. Season with salt and black pepper to taste.

Assemble Casserole: Pour the macaroni and cheese mixture into the prepared baking dish. Spread it out evenly.

Add Doritos Topping: Sprinkle the crushed Doritos evenly over the top of the casserole.

Bake: Bake in the preheated oven for 25-30 minutes, or until the casserole is bubbly and the Doritos are golden brown.

Garnish and Serve: Remove from the oven and let it cool for a few minutes before serving. Garnish with chopped fresh parsley if desired.