01 - Combine cold mashed potatoes, cheddar cheese, green onions, garlic powder, black pepper, salt, and 1 egg in a large bowl. Blend mixture until thoroughly integrated and uniform.
02 - Portion the mixture into heaping tablespoons and roll between hands to form balls approximately 1 1/4 inches in diameter. Arrange on a tray.
03 - Set up three separate bowls: one containing flour, one with beaten eggs, and one with breadcrumbs.
04 - Roll each potato ball in flour, dip into beaten eggs, then coat evenly in breadcrumbs. Transfer coated balls to a tray.
05 - Refrigerate the breaded potato balls for a minimum of 20 minutes to help retain their shape during frying.
06 - Pour vegetable oil into a deep fryer or heavy pot to a sufficient depth for frying. Preheat oil to 350°F (175°C).
07 - Working in batches, fry the chilled potato balls until golden brown and crispy, turning occasionally, for about 2 to 3 minutes per batch.
08 - Remove the fried balls with a slotted spoon and place on paper towels to drain excess oil. Serve immediately while hot.