1/2 cup unsweetened Dutch process cocoa
1 teaspoon baking soda
1/4 teaspoon baking powder
1/4 teaspoon salt
1 1/4 cups sugar
1/2 cup plus 2 tablespoons (1 1/4 sticks) room-temperature, unsalted butter
1 large egg
1/4 cup vegetable shortening
2 cups sifted confectioners’ sugar
2 teaspoons vanilla extract
1. Set two racks in the middle of the oven. Preheat to 375°F.
2. In a food processor, or bowl of an electric mixer, thoroughly mix the flour, cocoa, baking soda and powder, salt, and sugar. While pulsing, or on low speed, add the butter, and then the egg. Continue processing or mixing until dough comes together in a mass. (I don't have a food processor or an electric mixer, so I just stirred it with a spoon and then mixed it by hand.)
5. To assemble the cookies, in a pastry bag with a 1/2 inch, round tip, pipe teaspoon-size blobs of cream into the center of one cookie. 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.