Make sure that your leftover mac n cheese is nice and cold and set up (refrigerated for at least 12 hours). If needed, you can also freeze the macaroni just a bit before portioning out to coat with breading.
Preheat your oven to 425 degrees F (218 degrees C) and line a baking sheet (or two) with parchment paper. Use 1 tablespoon of the olive oil and a basting brush to coat the parchment paper lined baking sheet(s).
In a small bowl, whisk the eggs until well combined. Use a second bowl for the all-purpose flour and then a third small bowl to combine the breading ingredients: crushed Italian seasoned croutons, Italian seasoned Panko, and Parmesan cheese.
Using a table spoon, portion out large (approximately 1- 1 ½ inch) chunks of the leftover macaroni and cheese. Quickly roll in your palms to shape into a rough ball shape, then dip into the flour, then the egg mixture, and next into the breading mixture. Coat thoroughly and place on a parchment paper lined baking sheet. Repeat until all of your macaroni and cheese has been breaded.
Bake at 425 degrees F (218 degrees C) for about 10-12 minutes, then use the second tablespoon of olive oil to brush over the baking sheet. Roll the breaded macaroni and cheese balls to bake the opposite side for an additional 8-10 minutes. Remove from the oven and serve immediately.