01 - In a large mixing bowl, blend cold mashed potatoes, shredded cheddar cheese, green onions, garlic powder, black pepper, salt, and one egg until the mixture is fully cohesive.
02 - Scoop generous tablespoons of the potato mixture and shape into balls roughly 1 1/4 inches in diameter. Place formed balls onto a tray.
03 - Set out three shallow bowls: one with all-purpose flour, one with beaten eggs, and one with breadcrumbs.
04 - Carefully coat each ball in flour, then dip in beaten egg, and finally roll in breadcrumbs, ensuring an even, thorough coating.
05 - Arrange coated balls on a tray and refrigerate for a minimum of 20 minutes to firm up for frying.
06 - Pour vegetable oil into a deep fryer or heavy-bottomed pot to a depth suitable for submerging balls and heat to 350°F (175°C).
07 - Working in batches, lower the chilled potato balls carefully into hot oil. Fry for 2 to 3 minutes, turning occasionally, until they develop an even golden-brown exterior.
08 - Remove fried balls with a slotted spoon and transfer to paper towels to drain excess oil. Serve immediately while hot.