Preheat the oven to 375°F and lightly grease a 9×13-inch baking dish. Bring a large pot of salted water to a boil. Cook the elbow macaroni according to the package directions until just al dente, then drain and set aside. In a large saucepan over medium heat, melt the butter. Whisk in the flour and cook for about 1 minute, stirring constantly. Gradually whisk in the whole milk and heavy cream until smooth. Cook for 4–5 minutes, stirring frequently, until the sauce begins to thicken. Add the garlic powder, onion powder, smoked paprika, salt, and black pepper. Reduce the heat to low, then stir in the cheddar, mozzarella, Monterey Jack, and half of the Parmesan. Continue stirring until the cheeses melt into a smooth, creamy sauce.

Add the drained macaroni to the saucepan. Gently fold the pasta into the cheese sauce until every piece is evenly coated. Scrape along the bottom and sides of the pot so the sauce distributes evenly. Avoid cooking the sauce over high heat, as excessive heat can cause the cheese to become oily or grainy.

Transfer the macaroni mixture to the prepared baking dish and spread it into an even layer. Sprinkle the remaining Parmesan over the top, followed by extra shredded cheese if desired. Distribute the topping evenly so the cheese melts across the surface and creates a golden layer.

Bake for 20–25 minutes, until the casserole is hot and bubbly. For a more deeply golden top, broil for another 2–3 minutes, watching carefully to prevent the cheese from burning. Remove the dish from the oven and sprinkle with chopped fresh parsley. Let the mac and cheese rest for about 5 minutes before serving.