Bring a large pot of water to a boil, add a generous amount of salt, and cook the cavatappi according to the package directions until al dente. Drain the pasta and set it aside while you prepare the cheese sauce.

In a medium pot over medium heat, melt the unsalted butter. Once melted, whisk in the plain flour, fine salt, and ground black pepper to form a smooth roux. Continue whisking constantly for about 1-2 minutes to cook off the raw flour taste.

Gradually pour the milk and heavy cream into the roux, whisking constantly to prevent lumps. Cook the sauce over medium heat, whisking often, until it begins to bubble and thickens slightly. I like to keep an eye on the heat here to avoid scorching the milk—gentle bubbling is just perfect.

Reduce the heat to low and add the shredded sharp cheddar and mozzarella to the thickened sauce. Stir until both cheeses are fully melted and the sauce is smooth.

Add the cooked cavatappi from Step 1 to the pot of cheese sauce. Toss everything gently until all the pasta is well-coated. If the mixture is too thick, stir in an extra tablespoon or two of milk until you reach your desired consistency.

Allow the macaroni and cheese to sit for 5 minutes before serving so the sauce thickens up nicely. I always find waiting these few extra minutes makes the texture creamier and even more delicious!