Preheat oven to 350 F. Line two baking sheets with parchment paper. Set aside.

In a medium bowl, sift together flour, baking powder, baking soda, and salt. Set aside.

Beat butter in a large bowl. Add sugar and cocoa powder and beat until combined, about 3 minutes.

Add the eggs and vanilla and beat until combined.

On a low speed, alternately add the flour mixture and the milk in three additions, starting and ending with the flour. Mix until combined.

Scoop about two tablespoons worth of dough onto prepared baking sheet. Flatten into a 2-inch circle using an offset spatula. Leave a couple inches of space between each cookie as they will expand while baking.

Bake cookies for 12 minutes, until the edges of the cookies are set. Let cookies cool for 2 minutes on the baking sheet before transferring to a wire rack. It might be necessary to replace the sheets of parchment on the baking sheets between batches of cookies.

Let the cookies cool completely before frosting.

In a medium bowl, beat butter until cream. Alternately add in the powdered sugar and milk. Beat until the frosting is smooth but not runny, adding more powdered sugar or milk if needed. Stir in vanilla extract.

In a small bowl, beat butter until cream. Alternately add in the powdered sugar and milk. Beat until the frosting is smooth but not runny, adding more powdered sugar or milk if needed.

Add in cocoa powder and vanilla, beating until combined.

Stir in a desired amount of black food coloring.

Transfer frosting to a piping bag with a medium size round tip.

Using an offset spatula, frost all of the cookies with a layer of white frosting.

Using the chocolate frosting, pipe Jack Skellington’s eyes, nose, and mouth onto each cookie. Once the eyes have been outlined, fill in using the piping bag and smooth with an offset spatula.