Preheat oven to 375°F (190°C) and grease a muffin tin with non-stick spray.
In a bowl, mix mashed potatoes, cheddar cheese, sour cream, egg, garlic powder, salt, and pepper.
Scoop the mixture into the muffin tin, pressing slightly to form a cup shape.
Top each with crumbled bacon and Parmesan cheese.
Bake for 20-25 minutes, until golden brown and crispy on the edges.
Let cool slightly, then remove from the tin and garnish with chives before serving.