01 - In a large mixing bowl, thoroughly combine the cold mashed potatoes, cheddar cheese, green onions, garlic powder, black pepper, salt, and one large egg until the mixture is homogenous.
02 - Scoop out heaping tablespoons of the potato mixture and roll into balls approximately 1 1/4 inches in diameter. Arrange formed balls on a tray.
03 - Place flour in one bowl, beaten eggs in a second bowl, and breadcrumbs in a third bowl to create a breading station.
04 - Roll each potato ball in the flour, dip in the beaten eggs, then evenly coat with breadcrumbs. Ensure complete coverage.
05 - Transfer coated balls to a tray and refrigerate for at least 20 minutes to help set their shape for frying.
06 - Pour vegetable oil into a deep fryer or heavy-bottomed pot and heat to 350°F (175°C).
07 - Fry potato balls in batches, turning occasionally, until uniformly golden brown and crisp, approximately 2-3 minutes per batch.
08 - Remove fried balls with a slotted spoon and drain on paper towels. Serve immediately while hot.