01 - In a large mixing bowl, blend cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and one egg until homogenous.
02 - Scoop generous tablespoons of the mixture and form into balls approximately 1 1/4 inches in diameter. Arrange on a tray.
03 - Arrange three bowls: one holding flour, one with beaten eggs, and one containing breadcrumbs.
04 - Roll each potato ball in flour, dip into beaten eggs, then coat evenly with breadcrumbs.
05 - Place breaded balls on a tray and refrigerate for at least 20 minutes to firm.
06 - Preheat vegetable oil in a deep fryer or heavy-bottomed pot to 350°F (175°C).
07 - Working in batches, fry potato balls for 2 to 3 minutes per batch, turning gently until golden brown and crisp.
08 - Lift with a slotted spoon and transfer to paper towels to drain excess oil. Serve immediately while hot.