Homemade Oreos

1-¼ cup All-purpose Flour
½ cups Unsweetened Dutch Process Cocoa Powder
¼ teaspoons Baking Powder
1 teaspoon Baking Soda
¼ teaspoons Salt
1-½ cup Sugar
1-¼ stick Room Temperature, Unsalted Butter
1 whole Large Egg
¼ cups Room Temperature, Unsalted Butter
¼ cups Vegetable Shortening
2 cups Confectioner's Sugar
2 teaspoons Vanilla Extract

Preheat oven to 375 degrees with 2 racks in the middle of the oven.
In an electric mixer, thoroughly mix the flour, cocoa, baking soda and powder, salt, and sugar. On low speed, add the butter, then the egg. Mix until dough forms a mass.
Using a mini ice cream scoop, fill the scoop with batter, then place batter on a parchment-lined baking sheet. Leave approximately 2 inches between cookies. With damp hands, flatten the half balls of dough slightly. Bake for 9 minutes, rotating once for even baking. Set baking sheets on a rack to cool.
To make the cream, place butter and shortening in mixer. On low speed, gradually beat in the sugar and vanilla. Turn mixer on high for 2-3 minutes until filling is light and fluffy.
To make the sandwich cookies, fit a pastry bag with a 1/2 inch round tip and pipe blobs of cream onto the center of one cookie. Place another cookie of similar size on top of the cream. Lightly press together to work the filling to the edges of the cookie. Continue until all cookies have been made.