Preheat your oven to 350°. Spray your Donut Pan with non-stick spray.
In a large bowl whisk together the black cocoa, flour, brown sugar, baking powder, baking soda and salt. Set aside.
In a microwave safe bowl, measure out the chocolate chips.
Microwave the chocolate chips for 30 seconds and then stir. Repeat this step until the chocolate is completely melted.
Remove from the microwave and add your cold, diced butter to the melted chocolate. Stir until the butter has melted into the chocolate.
Add the chocolate mixture, egg, milk, vanilla and vinegar to the dry ingredients. Stir until well combined.
Transfer your donut batter to a piping bag or a large zip top bag and snip the corner.
Pipe the batter into the donut pan, making one circle in each cavity.
Bake at 350° for 10 minutes. The donuts will puff up, and rise while baking but should bounce back if you tap them when they are ready to come out of the oven.
Allow the donuts to rest in the pan for 5-10 minutes before turning the pan upside down onto a cooling rack to remove the donuts. If they get stuck, you may need to gently and carefully use a butterknife to loosen the edges.
Make the frosting by creaming the butter with either a stand mixer or electric hand mixture until smooth.
Slowly add in the powdered sugar and a little bit of heavy whipping cream (1/2 tbsp at a time) until all of the powdered sugar is added.
Add the vanilla extract, mixing until combined.
Add more whipping cream to adjust the consistency of the filling, if needed. You'll want the frosting to be thick.
Microwave the frosting for 15 seconds, or until warm and melted.
Add the frosting to a piping bag (you can use a large zip top bag with the corner cut, if needed).
Pipe the melted frosting onto the tops of each donut, making one pass over the top.
Add some chopped oreos to garnish.
Store in an air tight container for up to 3 days.