Root Beer Whoppie Pies

Steps

• 1

  Directions for batter: Position a rack in the center of the oven and preheat the oven to 375° F . Line two baking sheets with parchment paper.
• 2

  Sift together the flour, baking powder, and salt onto a sheet of waxed paper.
• 3

  In the work bowl of a stand mixer fitted with the paddle attachment, beat together the butter, shortening, and both sugars until light and cream, about 3 minutes. Add the eggs and the buttermilk and beat until combined.
• 4

  In a measuring cup, combine the mil, baking soda, and vinegar. Add the milk mixture to the batter along with the flour mixture and beat on low until just combined. Add the root beer and beat on medium for about 2 minutes until completely combined.
• 5

  Using a spoon, drop about 1 tablespoon of batter onto one of the prepared baking sheets and repeat, spacing them at least 2 inches apart. Bake one sheet at a time for about 10 minutes each, or until the cake begins to brown. Remove from the oven and let the cakes cool on the sheet for at least 5 minutes before transferring them to a rack to cool completely.
• 6

  Directions for Root Beer Marshmallow Frosting: In the work bowl of a stand mixer fitted with the paddle attachments, beat together the Marshmallow Fluff and the vegetable shortening, starting on low and increasing to medium speed until the mixture is smooth and fluffy, about 3 minutes. Reduce mixer speed to low, add the confectioners' sugar and the root beer, and beat until incorporated. Increase mixer speed to medium and beat until fluffy, about 3 minutes more.