Preheat the oven to 400 °F (200 °C) and grease a 24-cup mini muffin pan with cooking spray or softened butter.

In a large bowl, combine 3 cups of chilled mashed potatoes and 1 beaten large egg, stirring until smooth.

Stir in 1 cup shredded cheddar, ¼ cup chopped chives, ¼ cup flour, ½ tsp garlic powder, ½ tsp salt, and ¼ tsp black pepper until the mixture holds together.

Scoop out about 1 Tbsp of the mixture, roll into a ball, then coat evenly in ½ cup grated Parmesan.

Place each coated ball into a muffin cup and gently press to form a puff.

Bake for 15–20 minutes, until the muffins are golden brown and crisp on the outside.

Let cool in the pan for 5 minutes before removing. Serve warm.