In a large pot, bring water to a boil and cook the cavatappi according to the package instructions until al dente. Drain and keep the pasta aside.

In a medium saucepan, melt the butter over medium heat. Whisk in the flour, salt, and black pepper until it forms a roux.

Gradually pour in the milk and heavy cream, whisking until the mixture is well combined. Cook until it starts to bubble and thickens slightly.

Reduce the heat to low and stir in the cheddar and mozzarella cheeses. Mix until the cheese is fully melted and the sauce is creamy.

Add the cooked pasta to the sauce and stir until well combined. Adjust thickness by adding a tablespoon or two of milk if needed.

Let the mac and cheese sit for about 5 minutes to thicken slightly before serving.