In a medium-sized bowl, mix leftover mashed potatoes with crumbled bacon, salt, and pepper. If desired, add garlic powder.

With floured hands, scoop mashed potato into the palm of your hand. Flatten into a disk and add a cube of cheese to the center. Carefully form into a ball ensuring the cheese is completely covered with potatoes.

Add flour to a shallow dish. Scramble egg and 1-2 tablespoons of milk in another dish, and add breadcrumbs and grated parmesan to a third shallow dish. Dip each mashed potato ball in flour, then egg, then breadcrumbs. Repeat dipping back into the egg and then breadcrumbs for an extra crispy coating.

Add a single layer of mashed potato balls to the air fryer basket. Lightly spray balls with cooking oil.

Cook at 370 degrees Fahrenheit for 4 minutes, shake the basket, spray with additional oil as needed, and continue baking for 2-3 more minutes until golden brown. Be careful not to overcook to prevent the cheese from oozing out. Serve with ranch dipping sauce.