Chocolate Sandwich Cookies with Vanilla-Cream Filling
1 ¼ cups (175g) all-purpose flour
½ cup (45g) unsweetened Dutch process cocoa
1 teaspoon baking soda
¼ teaspoon baking powder
¼ teaspoon salt
1 ½ cups (300g) sugar
½ cup + 2 tablespoons (141g/1 ¼ sticks) room-temperature, unsalted butter
1 large egg
¼ cup (57g/½ stick) room-temperature, unsalted butter
¼ cup (57g) vegetable shortening
2 cups (280g) sifted confectioners' sugar
2 teaspoons vanilla extract
Set two racks in the middle of the oven. Preheat to 190ºC/375ºF.
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.
Take rounded teaspoons of batter and place on a parchment paper-lined baking sheet approximately 5cm (2in) apart. With moistened hands, slightly flatten the dough. Bake for 9 minutes (I baked mine for 10), rotating once for even baking. Set baking sheets on a rack to cool.
To make the cream, place butter and shortening in a mixing bowl, and at low speed, gradually beat in the sugar and vanilla. Turn the mixer on high and beat for 2-3 minutes until filling is light and fluffy.
To assemble the cookies, in a pastry bag with a 1.25cm (½ in) 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 process until all the cookies have been sandwiched with cream.