Red Velvet Mascarpone Whoopie Pie 

Make the cookies: Preheat the oven to 375 degrees F. Line 2 large baking sheets with parchment paper. Combine the semisweet and milk chocolate in a microwave-safe bowl and microwave at 50 percent power until melted, about 2 minutes. Whisk until smooth.

Whisk the melted butter, sour cream, eggs, vinegar, vanilla and food coloring in a bowl until combined. In another bowl, whisk the flour, sugar, cocoa powder, baking powder, baking soda and salt.

Add the flour mixture to the butter mixture in four equal batches, whisking each batch completely before adding the next. Stir in the melted chocolate.

Scoop heaping tablespoonfuls of batter onto the prepared baking sheets and smooth the tops with a damp finger. Bake until the cookies spring back when lightly pressed, 8 to 10 minutes. Let cool 10 minutes on the baking sheets, then transfer to racks to cool completely.

Meanwhile, make the filling: In a small pan, warm the cream over medium heat. Stir occasionally until cream is hot, but not simmering. Place chocolate in a heatproof bowl. Pour heated cream over the chocolate. Whisk until the chocolate melts.

Place in an ice bath until chilled, then cover with plastic wrap and refrigerate 4 hours, or up to overnight.

With an electric mixer, combine the mascarpone with half of the white chocolate mixture and whip for 2 minutes. Add remaining chocolate mixture and mix on high until frosting holds a peak.