Preheat oven to 350°.
Cream together the butter, granulated sugar and brown sugar.
Add the egg and vanilla. Mix until light in color and creamy.
Add in the dry ingredients (flour, black cocoa, crushed oreos, baking soda, baking powder and salt), mix into the dough. Mix until completely combined.
Portion out the dough into 1/2 cup portions. Roll into a ball and arrange 6 onto each cookie sheet. Press down slightly on the cookie dough, flattening it into what looks like a hockey puck.
Bake for 12-15 minutes, until the cookies are no longer glossy on the top.
Allow the cookies to cool on the pan for 20 minutes before frosting.
While the cookies are cooling, make the frosting by whipping the butter, cream cheese and vanilla until smooth.
Add the powdered sugar, one cup at a time.
Add milk a tsp at a time until you've reached your desired consistency, if needed.
Add the frosting to a gallon sized zip top bag, cut the corner of the bag and use it to pipe the frosting onto the warm cookies in a spiral.
Add extra crushed Oreos on top for garnish.
Serve warm. Store in and air tight container either in the fridge or on the counter.