Preheat your oven to 400°F. Line a baking sheet with parchment paper and lightly grease it with cooking spray or oil.
In a large mixing bowl, combine the cooled mashed potatoes, cheddar cheese, Parmesan cheese, flour, eggs, garlic powder, onion powder, salt, black pepper, and chives (if using). Mix until well combined.
Using a spoon or your hands, form the mixture into small balls, about 1 to 1.5 inches in diameter. Roll each ball in breadcrumbs to coat evenly.
Place the coated potato puffs on the prepared baking sheet, leaving some space between each puff.
Bake in the preheated oven for 20-25 minutes, or until the puffs are golden brown and crispy on the outside.
Remove from the oven and let cool for a few minutes before serving.