01 - In a large mixing bowl, thoroughly combine cold mashed potatoes, shredded cheddar cheese, finely chopped green onions, garlic powder, black pepper, salt, and one egg until fully blended.
02 - Scoop heaping tablespoons of the mixture and shape into balls approximately 1 1/4 inches in diameter. Arrange on a tray.
03 - Set up three bowls: the first with all-purpose flour, the second with beaten eggs, and the third with breadcrumbs.
04 - Roll each potato ball in flour, dip in beaten eggs, and coat with breadcrumbs, ensuring an even covering.
05 - Place breaded balls on a tray and refrigerate for at least 20 minutes to firm up.
06 - Fill a deep fryer or heavy-bottomed pot with vegetable oil and heat to 350°F (175°C).
07 - Fry potato balls in batches, turning occasionally, until golden brown and crisp, approximately 2 to 3 minutes per batch.
08 - Remove balls using a slotted spoon. Drain on paper towels and serve immediately while hot.