Leftover Mashed Potato Cheese Puffs Sometimes the best dishes come from giving yesterday’s leftovers a little makeover. These golden, cheesy potato puffs take humble mashed potatoes and transform them into something perfectly crisp on the outside, melty inside, and downright irresistible. What You'll Need Main Mixture: 2 cups cold or room-temperature leftover mashed potatoes 1 cup shredded cheddar cheese (sharp or medium) 1/2 cup shredded mozzarella cheese 1/4 cup grated Parmesan cheese 1/4 cup