Start by placing your cold leftover mashed potatoes in a large bowl. Mix in the sharp cheddar cheese, chopped chives, garlic powder, salt, and pepper until everything is well combined.

Using a 2 teaspoon cookie scoop, portion the mixture and roll it into balls around 1 inch in diameter. Arrange them on a prepared baking sheet. If too soft or sticky, refrigerate for 10-20 minutes.

Set up three shallow bowls for the flour, whisked eggs, and panko breadcrumbs. Dip each ball into the flour, then the egg, and finally roll in the panko breadcrumbs.

Heat oil in a small pot or deep skillet over medium-high heat until it reaches 375°F (190°C). Carefully add 3-4 potato balls and fry for about 2-3 minutes until golden brown.

Remove the fried balls from the oil using a slotted spoon and place them on a plate lined with paper towels to drain excess oil. Allow to cool slightly before serving.