Preheat oven to 350°F. Spray a donut pan with nonstick cooking spray that contains flour.
In a medium bowl, whisk the flour, cocoa, baking soda, baking powder, salt. Set aside.
In a stand mixer fitted with the paddle attachment mix the egg, vanilla, brown sugar, sour cream, and melted butter until smooth and combined.
Add the dry ingredients to the wet ingredients and mix until just combined. Batter will be thick!
Spoon batter into a ziplock bag that has the corner snipped off.
Pipe the batter into the donut pan, the cavities should be 2/3-3/4 full.
Bake for 8 mins or til a toothpick comes out with a few moist crumbs.
Remove from oven. Let cool in pan for 3-5 mins then turn out on a wire rack to cool for 15 minutes or until they have come closer to room temperature.