Grease the inside of the pan with non-stick cooking spray or butter.
Add the macaroni cheese, heavy cream, milk, salt, mustard powder, pepper, and nutmeg to the pan and stir to combine.
Place the pan into your air fryer and cook at 350 degrees F for 14 minutes. Stop the air fryer and stir the macaroni after 7 minutes.
Once the timer goes off, stir in the butter and cook for another 6 to 11 minutes.
Once the cooking time is up, stir the macaroni again and let it sit for a few minutes. The sauce will thicken as it cools.
Notes
After 25 minutes, if the pasta is not cooked, you can cook for an additional 2 minutes at a time until cooked al dente.
If you prefer a creamy mac and cheese, stir in up to an additional ½ cup of heavy cream after cooking. You can also use additional milk or cream to reheat leftovers on the stovetop.
The mustard flavor is fairly strong in this recipe and can be reduced to ½ teaspoon if desired.