01 - In a large mixing bowl, thoroughly blend cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and one egg until the mixture is smooth and cohesive.
02 - Scoop out heaping tablespoons of the potato mixture and roll firmly between your hands to form balls approximately 1 1/4 inches in diameter. Arrange on a tray.
03 - Set up three separate shallow bowls: one with all-purpose flour, one with the beaten eggs, and one with breadcrumbs.
04 - Roll each potato ball in the flour to coat, then dip in the beaten eggs, and finally roll in breadcrumbs until evenly covered. Return breaded balls to the tray.
05 - Refrigerate the coated potato balls for at least 20 minutes to ensure they maintain shape during frying.
06 - Fill a deep fryer or heavy-bottomed pot with vegetable oil and preheat to 350°F (175°F).
07 - Carefully lower potato balls into hot oil in batches. Fry while turning occasionally until golden brown and crisp, about 2 to 3 minutes per batch.
08 - Remove fried balls using a slotted spoon and transfer to a paper towel-lined tray to drain excess oil. Serve hot.