01 - Place cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and 1 egg into a large mixing bowl. Mix thoroughly until the ingredients are fully incorporated.
02 - Scoop heaping tablespoons of potato mixture and shape each portion into a ball about 1 1/4 inches in diameter. Arrange on a tray.
03 - Set up three shallow bowls: one with flour, one with beaten eggs, and one with breadcrumbs.
04 - Roll each potato ball in flour, dip in beaten eggs, then coat evenly with breadcrumbs.
05 - Transfer coated balls to a tray and refrigerate for at least 20 minutes to firm up.
06 - Pour vegetable oil into a deep fryer or heavy-bottomed pot to a depth of about 2 inches. Heat the oil to 350°F (175°C).
07 - Carefully add chilled potato balls to the hot oil in batches. Fry, turning occasionally, until golden brown and crispy, approximately 2 to 3 minutes per batch.
08 - Remove fried potato balls with a slotted spoon and drain on paper towels. Serve hot with preferred dipping sauces.