Preheat the oven to 375 F. Lightly grease or line with parchment paper 2 baking sheets. Make the cookies. Chop the milk chocolate into small pieces and then melt in a microwave-safe bowl in a microwave oven for about 2 minutes using 50% power. Whisk until smooth.

In a bowl, combine the melted butter, sour cream, eggs, vinegar, vanilla and food coloring. Mix well with a whisk. In another bowl, stir together the flour, granulate sugar, cocoa powder, baking powder, baking soda and salt. 

Divide the flour into 4 equal portions and whisk each batch with the butter mixture thoroughly until combined. Stir in the melted chocolate.

Using a cookie scooper or a rounded tablespoon, scoop heaping tablespoonfuls of cookie batter onto the prepared baking sheets. Dampen your finger with a little water and smooth the top of the cookies. Bake for about 8-10 minutes rotating the sheets halfway through. Allow the cookies to cool on the baking sheets for about 10 minutes before transferring to a wire rack.

In the meantime, make the filling. Using an electric mixer, beat the  cream cheese and butter until smooth. Slowly beat in the confectioners' sugar and then add the vanilla extract. Beat until there's a smooth consistency. Add a heaping tablespoonful of the finished filling in between 2 cookies. Repeat until all cookies and filling are used up. Chill in the refrigerator for about 30 minutes before serving. Enjoy!