In a large bowl use an electric mixer to cream together the butter and both sugars until fluffy. Beat in the egg, vanilla, vinegar, cocoa powder and food coloring.
Add in the flour, baking powder and salt; mix until just combined. The dough will be very crumbly.
Divide the dough into 6 equal portions and form each portion into a ball. Just until it comes together. Place on a parchment lined baking sheet and refrigerate for at *least* 30 minutes. (Do not skip this step, chilling is what makes the cookies soft and chewy in the middle).
Bake the cookies for 15-18 minutes at 350° F. The edges should just be turning golden brown, we want the cookies to stay chewy.
Allow the cookies to cool about 5 minutes on the baking sheet, then transfer to a wire rack to cool completely.
While the cookies are cooling, use an electric mixer to whip the butter and cream cheese until fluffy. Add in the powdered sugar and beat to combine. If desired, add a splash of milk to thin the frosting to your desired consistency.
Pipe the buttercream on top of the cookies using a large round tip and dust with cocoa powder.
Notes
Calories are automatically generated. For best results calculate based on your exact ingredients.*Food coloring gel will get you the most vibrant color (as pictured), but you can also use drops if preferred.