Preheat your oven to 350°F (175°C) and lightly grease a 9x13 inch baking dish with butter.

In a large pot of boiling salted water, cook the elbow macaroni until slightly al dente. Drain and set aside.

In a large saucepan, melt the unsalted butter over medium heat. Whisk in the flour and cook for 1-2 minutes to create a roux.

Slowly add the whole milk to the roux while whisking continuously, then introduce the heavy cream, stirring until smooth and slightly thickened.

Stir in the salt, black pepper, dry mustard powder, and smoked paprika until evenly combined.

Gradually add 3 cups of shredded sharp cheddar cheese to the saucepan, stirring until melted and the sauce is creamy.

Add the cooked macaroni to the cheese sauce, stirring gently to coat evenly.

Pour the macaroni and cheese mixture into the prepared baking dish and sprinkle the remaining 1 cup of cheddar cheese over the top.

If using breadcrumbs, sprinkle them evenly over the cheese layer.

Bake for 20-25 minutes until bubbly and golden brown.

Let it rest for a few minutes before serving to allow the cheese sauce to set.