Preheat oven to 400 degrees F. Spray 12 muffin cups generously with nonstick cooking spray. *Very important to spray the pan well to avoid sticking; greasing with butter or vegetable shortening works too.
In a large bowl, combine ingredients.
Divide the potato mixture evenly into the 12 muffin cups.
Bake in the preheated 400 degree oven for 30-35 minutes. Cool slightly before removing each mashed potato puff from its cup. Use a thin knife to loosen if necessary.
Garnish with sour cream, chopped chives, cheese and bacon if desired.