Red Velvet Whoopie Pies

Preheat the oven to 350°F. Line two half-sheet pans with parchment paper.

Sift together the flour, cocoa powder, baking powder, baking soda, and salt into a bowl, and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, cream the butter, brown sugar, and oil until light and fluffy. Add the egg and mix until well incorporated. Add the flour mixture, alternating with the buttermilk and food coloring, in three additions.

Fill a pastry bag with a plain tip (such as Ateco #806) and pipe rounds about 1½ inches in diameter onto the prepared pans, leaving a 1-inch space between cookies. Bake for 6 to 9 minutes, or until a cookie springs back slightly when pressed in the center. Cool completely on wire racks before filling.