These classic chocolate gluten free whoopie pies are a simple sandwich of cakey chocolate cookie pies filled with a sweet, creamy sandwich cookie filling. Super fun, and no special equipment needed!
Preheat your oven to 350°F. Line rimmed baking sheets with parchment paper and set them aside.
In a large bowl, place the flour, xanthan gum, cocoa powder, baking soda, baking powder, salt and sugar. Whisk to combine, working out the lumps in the brown sugar.
Add the butter and shortening, and mix with a fork until crumbly and lumpy. Add the egg and vanilla, and mix to combine. Add the milk, and mix until uniformly smooth.
Place the batter in a piping bag fitted with a plain open piping tip about 1/2-inch in diameter. Pipe batter in rounds about 1 1/2 inches in diameter onto the prepared baking sheets, at least an inch apart. They will spread a bit while baking.
Place one baking sheet at a time into the center of the preheated oven and bake until they spring back when pressed gently in the center, 8 to 10 minutes.
Remove from the oven and allow the cakes to cool for about 10 minutes before transferring to a wire rack to cool completely.
When removing the cakes from the parchment paper, it is best to peel away the parchment paper from the back of the cake, rather than attempting to lift the cake right off the paper.
Once the cookies are completely cool, pair the cookies that appear the most like one another (a memory game!).
Add about a tablespoon of filling either with a pastry bag fitted with a star tip or with a spoon or knife, and close. Serve chilled or at room temperature.