In a large bowl, whisk together the flour, baking powder, baking soda, salt, and cocoa powder.

In a mixer, cream together the brown sugar and the butter until fully combined. Slowly mix in the vanilla, then the egg, then the melted chocolate.

Slowly add in the flour mixture a little at a time until fully combined. Chill in the refrigerator for at least one hour.

Preheat your oven to 350 degrees. Line a baking sheet with parchment paper or a silicon mat and set aside.

Make one inch sized dough balls and space them approximately two inches apart. Push them down lightly and bake for 7 to 10 minutes, rotating the pan halfway through baking.

Let cool on the pan for about two minutes before cooling completely on a wire rack.

Let the cookies cool completely before spreading pumpkin buttercream frosting between them and making a cookie sandwich.

Store in an airtight container.