Red Velvet Whoopie Pies

Heat oven to 375 degrees F. Line baking sheets with parchment paper. In a medium bowl, whisk together the flour, cocoa, baking soda, and salt. Using an electric mixer, beat the sugar and butter in a large bowl until light and fluffy, about 3 minutes. Beat in the eggs, then the vanilla and food coloring. Alternately add the flour mixture and buttermilk, mixing just until incorporated. Drop level tablespoons of the batter onto the prepared baking sheets, spacing them 2 inches apart. Bake until the tops are set and spring back when lightly pressed, 6 to 8 minutes. Let cool on the baking sheets for 5 minutes, then transfer to a wire rack and let cool completely. While the cookies cool, using an electric mixer, beat the cream cheese until smooth. Add the marshmallow cream and beat until fluffy, about 3 minutes. Spread 1 level tablespoon of filling onto half of the cookies, then sandwich with the remaining cookies. Sprinkle sanding sugar around the edges of the whoopie pies. Serve immediately or refrigerate, in a single layer, covered, for up to 5 days. Bring to room temperature before serving.