Cook the elbow macaroni in salted boiling water according to package directions until tender, then drain and set aside.
Melt the butter in a large saucepan over medium heat, then add the milk and heavy cream and bring to a gentle simmer.
Reduce heat to low, add the cheddar and Parmesan cheese, and stir constantly until the cheese melts into a smooth sauce.
Add the cooked macaroni and salt to the cheese sauce and stir until the pasta is evenly coated and creamy.
Serve immediately while hot for the best restaurant-style texture and flavor.
