1 batch macaroni and cheese, prepared as directed and well chilled (1 box store-bought or your favorite homemade recipe, I used one 5.5-ounce box Kraft)
1/2 cup all-purpose flour
2 large eggs, beaten
about 1 cup breadcrumbs (seasoned if preferred; I used Trader Joe's which are unseasoned)
4 tablespoons olive oil, divided
Prepare mac 'n cheese according to package directions. Place in an airtight container and refrigerate for at least 12 hours, up to 3 days; I made these after 2 days. Chilling the mac 'n cheese is an instrumental step and cannot be skipped because the cheese needs to congeal, solidify, and dry out a bit prior to baking the cheese balls. You may be able to speed this process up and shortcut it a bit by freezing the cooked mac 'n cheese, but I have not tested it.
About 15 minutes prior to preparing the cheese balls, place the container of mac 'n cheese in the freezer for a quick cold blast. Meanwhile, place flour, eggs, and breadcrumbs in 3 separate small bowls; set aside.
Preheat oven to 425F and line two baking sheets with Silpats, parchment paper, or aluminum foil (line baking sheets with something to save yourself cleanup work). Drizzle 1 tablespoon olive oil on each baking sheet, smear it around with your hands; set baking sheets aside.
Remove mac 'n cheese from the freezer and using a 1-inch cookie scoop or tablespoon-sized scoop, portion out and shape the balls, taking care not to make them larger than about 1-inch in diameter because after battering and breading, they become much larger in size. Depending on the type of noodles in your mac 'n cheese, how cold, or how cheesy the mac 'n cheese is, lightly hand-shaping the noodles into balls may be necessary rather than replying solely on a cookie scoop. Roll each ball through the flour, dip briefly in the egg, roll it through the breadcrumbs, and place it on baking sheet. Repeat until all balls have been battered, placing about 10 balls per baking tray.
Bake for 10 minutes (don't be surprised if your smoke detector goes off), remove trays from oven and add 1 tablespoon of oil to each tray and smear it around, flip balls over, and bake for 7 to 10 minutes, or until browned and golden. Remove from the oven and serve immediately; optionally serve with Homemade Spicy Mustard, prepared mustard, ketchup, chipotle mayo, or a favorite condiment.