Preheat oven to 375°F. Spray 2 mini muffin pans (or use 1 pan twice) with cooking spray.
Stir together the mashed potatoes, egg, ¾-cup cheddar cheese, and 2 tablespoons chopped bacon. Using a spoon, scoop potato mixture into cups, packing the potatoes down into each cup. Bake for 30-35 minutes or until golden brown and crisp around the edges.
Remove pan from the oven, top the potato mixture with the remaining ¼-cup cheddar cheese and return to the oven for 3 more minutes.
Remove pan from the oven and transfer to a rack. Let potatoes cool for 5 minutes.
Using a knife or mini metal spatula, transfer to a rack. Let potatoes cool for 5 minutes.
Sprinkle with chopped chives. Serve immediately.
