Preheat your oven to 350°F (175°C). Prepare two baking sheets by lining them with parchment paper to prevent sticking.

Mix the dry ingredients in a bowl. Combine all-purpose flour, black cocoa powder, baking powder, baking soda, and kosher salt.

Combine the wet ingredients in another container. Whisk together buttermilk, white vinegar, and red food coloring until the color is even.

Cream the softened butter and sugar together until fluffy, then add the egg and vanilla extract, mixing well.

Gently add half of the dry ingredients into the butter mixture, then pour in the buttermilk mixture, followed by the rest of the dry ingredients.

Pipe the batter onto prepared baking sheets, creating 2-inch circles. Smooth the tops with a spatula if necessary.

Bake for about 8 minutes, watching closely until they spring back when touched. Let the cookies cool completely.

Beat the filling ingredients until smooth. Gradually add powdered sugar, beating until creamy.

Assemble the whoopie pies by pairing cookies. Pipe a generous amount of the cream filling onto one cookie and sandwich it with another.