01 - In a large mixing bowl, thoroughly combine the cold mashed potatoes, shredded cheddar cheese, finely chopped green onions, garlic powder, black pepper, salt, and one large egg until the mixture is even.
02 - Portion out heaping tablespoons of the mixture and roll each into a smooth ball approximately 1 1/4 inches in diameter. Arrange on a tray.
03 - Arrange three separate bowls: one containing all-purpose flour, another with beaten eggs, and a third with breadcrumbs.
04 - Roll each ball first in flour, then dip into the beaten eggs, and finally coat evenly with breadcrumbs. Place coated balls back on the tray.
05 - Refrigerate the breaded potato balls for at least 20 minutes to help them firm up and retain their shape during frying.
06 - Fill a deep fryer or heavy-bottomed pot with vegetable oil and heat to 350°F (175°C).
07 - Working in batches, carefully lower the chilled potato balls into the hot oil. Fry for 2–3 minutes per batch, turning occasionally until evenly golden and crisp.
08 - Remove the fried potato balls with a slotted spoon and drain on paper towels. Serve immediately while hot.