Preheat oven to 400°F (200°C) and generously grease a 12-cup standard muffin tin.

In a large mixing bowl, combine the cold mashed potatoes, shredded cheddar cheese, beaten eggs, and sour cream until the mixture is uniform.

Fold in the chopped chives, garlic powder, salt, and pepper.

Distribute the potato mixture evenly among the 12 muffin cups, filling each cup to the top.

Bake for 20 to 25 minutes until the puffs are golden brown on the surface and firm to the touch.

Remove from the oven and allow the puffs to cool in the tin for 5 minutes to ensure they set before service.