Preheat your oven to 200°C (400°F). Lightly grease a 12-cup muffin tin with nonstick spray or melted butter.

Boil the peeled and cubed potatoes in a medium pot of salted water until fork-tender, about 12-15 minutes. Drain well.

Mash the hot potatoes in a large mixing bowl. Add the butter and milk, mashing until smooth and creamy.

Stir in the cheddar cheese, half of the grated parmesan, salt, black pepper, and chives if using. Allow the mixture to cool slightly.

Lightly beat the eggs in a small bowl, then add to the potato mixture, mixing until fully incorporated.

Divide the mixture evenly among the muffin tin cups, filling each about three-quarters full.

Sprinkle the tops with the remaining parmesan cheese.

Bake for 20-25 minutes, or until the tops are golden brown and the puffs are set.

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