01 - In a large bowl, mix cold mashed potatoes, shredded cheddar cheese, green onions, garlic powder, ground black pepper, salt, and one egg until evenly blended.
02 - Scoop heaping tablespoons of the mixture and roll between palms to shape balls about 1 1/4 inches in diameter. Arrange on a tray.
03 - Prepare three separate bowls: one with flour, one with beaten eggs, and one with breadcrumbs.
04 - Roll each potato ball in flour, dip in beaten eggs, and coat thoroughly with breadcrumbs.
05 - Place the prepared balls on a tray and refrigerate for a minimum of 20 minutes to ensure they maintain their shape during frying.
06 - Preheat vegetable oil in a deep fryer or heavy-bottomed pot to 350°F.
07 - Fry the balls in batches, turning as needed, until evenly golden and crisp, approximately 2 to 3 minutes per batch.
08 - Remove from the oil using a slotted spoon and drain briefly on paper towels. Serve the balls hot.