Preheat your oven to 400°F (200°C) and lightly grease a muffin tin with butter or oil.
In a large bowl, combine the mashed potatoes, cheddar cheese, eggs, flour, and green onions. Mix until well combined.
Season the mixture with salt and pepper to taste.
Spoon the potato mixture into the prepared muffin tin, filling each cup about 3/4 full.
Sprinkle the tops with grated Parmesan cheese.
Bake in the preheated oven for 20-25 minutes, or until the tops are golden brown and crispy.
Allow the puffs to cool slightly before removing them from the tin. Serve warm.
Variations & Tips

For a bit of spice, add a pinch of cayenne pepper or some chopped jalapeños to the potato mixture. You can also experiment with different cheeses, such as mozzarella or pepper jack, for a unique flavor. If you have picky eaters, try adding some finely chopped cooked bacon or ham for extra protein. For a gluten-free version, substitute the flour with almond flour or gluten-free flour blend. These puffs are versatile and can be customized to suit your family’s taste preferences.