01 - In a large mixing bowl, thoroughly blend cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and 1 egg until fully incorporated.
02 - Scoop heaping tablespoons of the mixture and roll between palms to shape balls approximately 1 1/4 inches in diameter. Arrange on a tray.
03 - Set up three shallow bowls: one holding all-purpose flour, one containing the beaten eggs, and another with breadcrumbs.
04 - Roll each ball in flour to coat evenly, then dip into the beaten eggs, followed by a generous coating of breadcrumbs. Return to the tray.
05 - Transfer the tray to the refrigerator and chill for at least 20 minutes to firm up and retain shape during frying.
06 - Pour vegetable oil into a deep fryer or heavy-bottomed pot and heat to 350°F (175°C).
07 - Fry mashed potato balls in batches, turning occasionally, until golden brown and crisp, about 2–3 minutes per batch. Avoid overcrowding the pot.
08 - Remove balls with a slotted spoon and transfer to a paper towel-lined plate to drain excess oil. Serve immediately while hot.