Preheat oven to 350°F. Spray a donut pan with nonstick cooking spray that contains flour.
In a medium bowl, whisk the flour, black cocoa powder, Oreo crumbs, baking soda, baking powder, salt. Set aside.
In a stand mixer fitted with paddle mix the egg, egg yolk, 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 very thick.
Spoon batter into a Ziplock bag or piping bag that has the corner snipped off.
Pipe the batter into the donut pan, the cavities should be ½ full. (The donuts will rise a lot).
Bake for 7-8 mins or until 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 and let the donuts cool completely before frosting.