Using your leftover refrigerated macaroni and cheese, take large chunks, about 2 Tbsp, and roll into balls. Set aside.
In a bowl, add egg and milk and whisk to combine. Then in another bowl, add panko breadcrumbs, salt, garlic powder, paprika, and chopped bacon if using, and stir to combine.
Grab a macaroni and cheese ball and place in egg and milk mixture, coating the entire ball, then add to the panko mixture, then add to a lined parchment paper cookie sheet. Place in the freezer and freeze for 30 minutes.
Preheat your air fryer on 360 degrees. After the 30 minutes, remove the macaroni and cheese balls from the freezer and place them into air fryer basket in a single layer, making sure they don’t touch. Air fry for 8-10 minutes until light and golden on the outside. Remove, serve, and enjoy.