01 - In a large mixing bowl, thoroughly blend cold mashed potatoes, shredded cheddar cheese, finely chopped green onions, garlic powder, black pepper, salt, and one egg until fully incorporated.
02 - Scoop generous tablespoons of the potato mixture and roll each into a ball measuring approximately 1 1/4 inches in diameter. Arrange balls on a tray in a single layer.
03 - Set up three shallow bowls: one with all-purpose flour, one with beaten eggs, and one with breadcrumbs.
04 - Roll each potato ball in flour, dip into the beaten eggs, and then coat thoroughly with breadcrumbs, ensuring an even layer.
05 - Position the coated balls on a tray and refrigerate for a minimum of 20 minutes to help them hold their shape during frying.
06 - Heat vegetable oil in a deep fryer or heavy-bottomed pot to 350°F (175°C), using a thermometer for accuracy.
07 - Fry balls in batches, turning occasionally, until golden brown and crisply textured, about 2 to 3 minutes per batch.
08 - Use a slotted spoon to transfer fried potato balls to a plate lined with paper towels. Allow excess oil to drain. Serve immediately while hot.