01 - In a large mixing bowl, blend cold mashed potatoes, shredded cheddar cheese, chopped green onions, garlic powder, black pepper, salt, and one egg until homogeneous.
02 - Portion the potato mixture into heaping tablespoons and roll into 1 1/4-inch balls; arrange them on a tray.
03 - Set up three bowls: one with flour, one with beaten eggs, and one with breadcrumbs.
04 - Coat each potato ball first in flour, then dip into the beaten eggs, and finally roll thoroughly in breadcrumbs.
05 - Place breaded balls onto a tray and refrigerate for a minimum of 20 minutes to firm.
06 - Preheat vegetable oil in a deep fryer or heavy-bottomed pot to 350°F (175°C).
07 - Fry balls in batches, turning occasionally, for 2–3 minutes until golden and crisp. Do not overcrowd the pot.
08 - Transfer fried balls to a plate lined with paper towels to drain excess oil. Serve immediately while hot.