Combine the first 4 ingredients in a large saucepan over medium heat, stirring frequently; cook until smooth. Remove from heat; stir in macaroni. Serve immediately.
Processed cheese is a must in this quintessential quick-and-easy dish. It melts easily and gets smooth and creamy without help from flour, eggs, or other ingredients used in fancier counterparts. You can make prep even simpler by heating the first four ingredients in the microwave for about 3 minutes in a covered dish instead of cooking them on the stovetop.