Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper and lightly spray with cooking spray or oil.
In a large mixing bowl, combine the mashed potatoes, shredded cheddar cheese, and grated Parmesan cheese. Mix until well combined.
Add the eggs, flour, garlic powder, onion powder, salt, and black pepper to the potato mixture. Stir until everything is well incorporated, and you have a thick batter.
Using a spoon or small ice cream scoop, scoop out portions of the mixture and drop them onto the prepared baking sheet, leaving space between each puff.
Lightly spray the tops of the puffs with cooking spray or brush with oil.
Bake in the preheated oven for about 20-25 minutes, or until the puffs are golden brown and crispy on the outside.
Remove from the oven and let cool slightly before serving.