01 - Combine cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and 1 egg in a large mixing bowl. Mix thoroughly until uniformly blended.
02 - Scoop heaping tablespoons of the mixture and roll into evenly shaped balls, approximately 1 1/4 inches in diameter. Transfer to a tray.
03 - Prepare three separate bowls: one containing flour, one with beaten eggs, and one with breadcrumbs.
04 - Dredge each potato ball in the flour, dip into the beaten eggs, then roll to coat thoroughly in breadcrumbs.
05 - Arrange coated balls on a tray and refrigerate for at least 20 minutes to firm up and maintain their shape during frying.
06 - Pour vegetable oil into a deep fryer or heavy-bottomed pot and heat to 350°F (175°C).
07 - Fry the potato balls in batches, turning occasionally, until crisp and deeply golden brown, about 2–3 minutes per batch.
08 - Remove fried balls with a slotted spoon and drain on paper towels. Serve hot for optimal texture.