Cook the macaroni according to the al dente directions on the package. If not included, remove the pasta 1 to 2 minutes earlier than indicated. Drain the pasta, return it to the pot, and set aside.
Make the cheese sauce:
In a small bowl, whisk ½ cup of milk and the 2 tablespoons of flour until there are no visible lumps and set aside.
In a medium saucepan over medium heat, warm the remaining 1 cup of milk. Once you begin to see steam rising from the milk, whisk in the flour and milk mixture and continue whisking for about 2 minutes until the milk thickens slightly. It will feel and look like heavy cream.
Reduce the heat to low, add the shredded cheese, and continue to use the whisk to combine the cheese with the milk. Add the salt and dijon mustard, and continue to stir for about 2 more minutes until all the cheese has melted and the sauce is rich and creamy. Turn off the heat.
Combine:
Pour the cheese sauce over the cooked macaroni and stir to combine. Serve immediately.
Storage:
Leftovers, once cooled, can be refrigerated in an airtight container for up to a week. To reheat, add a splash of milk to the macaroni and cheese and the sauce will be creamy again!
Notes
For best results, use whole or 2% milk for this recipe -1% milk, at a minimum.