01 - In a large mixing bowl, thoroughly combine cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and one egg until homogeneous.
02 - Scoop 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 - Fill three separate bowls: one with flour, one with beaten eggs, and one with breadcrumbs (panko or regular).
04 - Dredge each potato ball first in flour, then immerse in beaten egg, and finally coat thoroughly in breadcrumbs.
05 - Transfer coated balls to a tray and refrigerate for at least 20 minutes to firm them and help maintain their shape during frying.
06 - Pour vegetable oil into a deep fryer or heavy-bottomed pot, ensuring oil depth covers the balls fully. Heat the oil to 350°F (175°C).
07 - Fry the potato balls in small batches, turning occasionally, until uniformly golden brown and crisp, approximately 2 to 3 minutes per batch.
08 - Remove each batch with a slotted spoon and set on paper towels to absorb excess oil. Serve the balls hot.