Red Velvet Whoopie Pies

For the Cookies:
1.5 oz semisweet chocolate, chopped
12 tablespoons unsalted butter, melted
1/2 cup sour cream
2 large eggs
1 1/2 teaspoons apple cider vinegar
1/2 teaspoon vanilla extract
1 tablespoon red food coloring
2 1/4 cups all-purpose flour
1 cup granulated sugar
1/4 cup unsweetened cocoa powder
2 teaspoons baking powder
1/4 teaspoon baking soda
1/2 teaspoon salt

For the Filling:
8 ounces cream cheese, at room temperature
3 tablespoons unsalted butter, at room temperature
2 1/2 cups confectioners' sugar, sifted
1 vanilla bean, halved lengthwise and seeds scraped

To 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:
-Beat the cream cheese and butter with a mixer until smooth. Beat in the confectioners' sugar and vanilla seeds. Sandwich a heaping tablespoonful of filling between 2 cookies; repeat with the remaining cookies and filling. Refrigerate 30 minutes before serving.