01 - Combine cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and one egg in a large mixing bowl. Mix thoroughly until homogeneous.
02 - Portion the mixture into heaping tablespoons and roll each into a smooth ball approximately 1 1/4 inches in diameter. Arrange on a tray.
03 - Set out three shallow bowls: fill one with flour, one with beaten eggs, and one with breadcrumbs.
04 - Coat each potato ball first in flour, then dip into beaten eggs, and finally roll in breadcrumbs to ensure an even coating.
05 - Place breaded balls on a tray and refrigerate for at least 20 minutes to firm and set their shape.
06 - In a deep fryer or heavy-bottomed pot, heat vegetable oil to 350°F (175°C).
07 - Working in batches, fry the balls for 2 to 3 minutes per batch, turning until all sides are golden brown and crisp.
08 - Remove fried balls using a slotted spoon, transferring to paper towels to drain excess oil. Serve immediately while hot.