In a large bowl cream together the butter and sugar using an electric mixer (or use a stand mixer) until well combined.

Add the egg and vanilla to the butter mixture and stir well.

In a separate medium-sized bowl, whisk together the flour, black cocoa powder, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until well combined.

Divide the dough into two equal parts, form each into a disk about 1" thick, and wrap in plastic wrap. Chill for at least 1 hour before proceeding.

Preheat the oven to 350°F (175°C) and line cookie sheets with parchment paper. Set aside.

Working with one disc of dough at a time, unwrap dough and transfer to a clean, lightly floured surface. Lightly sprinkle flour over the dough and use a rolling pin to roll the dough to about ⅛-1/16" (0.2cm) thickness.

To make the pattern shown on my cookies: take a clean, grid-patterned cooling rack and flip it upside down. Gently press into the cookie dough, then gently lift, rotate the cooling rack, and press again before gently lifting and removing.

Use a small round cookie cutter (I use 1 ¾" (4.5cm) circles) to cut out circles and transfer to baking sheet, spacing 1” (2.5cm) apart.

Once you’ve made as many cuts as possible, be sure to recombine the dough scraps, roll out again, and cut out more cookies to maximize the dough yield.

Bake the cookies in the preheated oven for 8-10 minutes. Allow them to cool completely before filling.

In a medium-sized bowl, cream together the softened unsalted butter and shortening using an electric mixer.

Gradually add the powdered sugar, stirring until well-combined.

Stir in vanilla extract and salt.

Pipe or spread a thin layer of the filling on the flat side of a cooled cookie, and then sandwich with another cookie, flat side down.

Repeat with the remaining cookies and filling. Enjoy!