1.In a medium-sized bowl, mix the flour, cocoa, baking soda and powder, salt, and sugar.
2.Beat in the butter and the egg. Continue mixing until dough comes together in a mass.
3.Take rounded teaspoons of batter and place on a parchment paper-lined baking sheet approximately 2 inches apart. With moistened hands, slightly flatten the dough. (I found that while the dough wasn't sticky enough to roll, I could press it flat with my hands like the recipe said and then use cookie cutters to cut perfect circles. If you just care about the taste, then there is no need for the cookie cutters. Also, remember this is a chance to get creative and use all kinds of cookie cutters.).
4.Bake for 9 minutes at 375°F Set on a rack to cool.
For the filling:.
1.Place butter and shortening in a mixing bowl, and at low speed, gradually beat in the sugar and vanilla.
2.Turn the mixer on high and beat for 2-3 minutes until filling is light and fluffy.
3.To make a cookie, pipe teaspoon-sized blobs of cream into the center of a cookie using a pastry bag with a 1/2 inch round tip. (If you don't have a pastry bag, you could easily just spread the filling with a knife or use a Ziplock with the corner cut off as a pastry bag. I had a pastry bag, but I only had a star tip. The tip doesn't matter much.).
4.Place another cookie, equal in size to the first, on top of the cream. Lightly press, to work the filling evenly to the outsides of the cookie. Continue this process until all the cookies have been sandwiched with cream. (If you do this really fast, it will look like you are spinning records. See above.).
5.Eat the cookies using whatever method you prefer. I like the take apart, lick the cream, then eat the cookie method. Be sure to save some to make oreo cupcakes!