How to Make It
Preheat oven to 400°F. Coat a donut pan with cooking spray.
Whisk together egg and egg white vigorously in a medium bowl until fluffy. Whisk in flour and baking powder until combined. Stir in potatoes until fully incorporated.
Fill a large piping bag or ziplock plastic bag with potato mixture, and pipe into prepared donut pan.
Bake in preheated oven until donut is dry to touch but also soft when pressed, about 20 minutes. Set pan on a wire rack, and cool 10 minutes, then invert donuts directly onto wire rack. Place gravy in a shallow dish. Dip the top of each donut into gravy, and serve!