Preheat the oven to 375°F (190°C). Grease a 9×13-inch baking dish.

Cook the macaroni in a large pot of salted boiling water until just al dente. Drain and set aside.

In a large saucepan over medium heat, melt the butter. Whisk in the flour and cook for about 1–2 minutes to form a roux.

Gradually whisk in the milk and heavy cream, stirring constantly until smooth. Continue stirring as the mixture simmers and thickens (about 5 minutes).

Stir in salt, pepper, garlic powder, and smoked paprika (if using). Remove from heat.

Add 3 cups of cheddar and 1 cup of mozzarella to the sauce, stirring until fully melted and smooth.

Mix the cooked macaroni into the cheese sauce, ensuring each piece is coated.

Transfer half the macaroni-and-cheese mixture into the prepared baking dish. Sprinkle half the remaining cheddar and mozzarella over it. Layer the rest of the macaroni-cheese mixture on top, then finish with the remaining cheese to form a cheesy top layer.

Bake uncovered for 20–25 minutes, until the top is bubbly and turns golden.

Let rest for about 5 minutes before serving so the sauce sets slightly for creamy texture.