Heat oven to 375 degrees. Line sheets with parchment paper.In Medium bowl mix flour, cocoa,baking soda and salt. Using an electric mixer, beat sugar and butter in large bowl until fluffy. Beat in eggs, then vanilla and food coloring. Alternately add flour mixture and buttermilk just until incorporated. Drop level T. of batter onto 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. Move to cooling racks and cool completely. While cookies cool, beat the cream cheese until smoooth. Add marshmallow cream until fluffy, about 3 minutes. Spread 1 T. of filling onto half of the cookies, then put other side on top. Sprinkle with sanding sugar around the edges of the woopie pies. Serve immediatlely or refigerate, in a single layer, covered for up to 5 days. Bring to room temperature before serving. Makes 24 cookies. Wilton sugar has pretty sanding sugar for the edges or use whatever you would like to use.