Preheat oven to 350°F. Grease a 9x13-inch baking pan with butter or nonstick spray. Set aside.
Cook the pasta al dente according to the package directions. Drain and rinse well under cold water to remove excess starch so the pasta doesn't overcook and to cool it down. Set aside.
1 pound dry elbow macaroni
In a large pot or Dutch Oven, over medium heat, melt the butter. Add in the garlic and cook until fragrant, about 30-60 seconds.
6 tablespoons unsalted butter, 2 cloves garlic
Whisk in the flour and cook for 1-2 minutes.
⅓ cup all-purpose flour
Slowly whisk in the milk, then add in the cream, mustard powder, and bring to a simmer. Stirring often, cook until the mixture has thickened.
3 cups whole milk, 1 cup heavy cream, ½ teaspoon dry mustard powder
Turn off the heat and stir in the cheeses until melted. Add in the pasta and toss until well coated in the sauce. Taste and season with salt and pepper as needed.
3 cups freshly shredded sharp cheddar cheese, 2 cups freshly shredded Gruyere cheese, ½ cup freshly shredded Parmesan cheese, Kosher salt and freshly ground black pepper
Transfer the mixture to your prepared baking dish.
In a medium bowl, stir together the panko, melted butter, and paprika. Sprinkle evenly over the mac and cheese.
1½ cups panko breadcrumbs, 4 tablespoons unsalted butter, ¼ teaspoon ground paprika
Bake for 20-30 minutes, or until the casserole is bubbly and the top is golden brown, or broil for a few minutes for an extra crispy crust.
Let the casserole cool in the baking dish for 10 minutes before serving. Garnish with parsley and enjoy!
chopped fresh parsley