Sift the flour, 39 g deZaan Holland Carbon Black 10/12% Dutched Cocoa Powder, baking powder, and salt together. Set aside.
Cream the butter and granulated sugar until light and fluffy.
Add in the egg and 10 g Prova Gourmet Madagascar Bourbon Vanilla Extract. Mix to combine. Add in the dry ingredients and mix on low until just combined. Do not over-mix.
Divide the dough in two. Roll each portion between two pieces of parchment to 0.6 cm/0.25 inch thickness.
Cut the dough into desired shape and size. Chill the sheets until firm. This will make it easy to separate the pieces.
Lay out the cookies onto parchment-lined sheet trays. Space them about 2.5 cm/1 inch apart.
Bake at 176°C/350°F for about 12-15 minutes.
To make the filling, combine 9 g Prova Gourmet Madagascar Bourbon Vanilla Bean Paste with the rest of the ingredients in the bowl of a stand mixer. With a paddle, cream until smooth.
Roll the batter out between two pieces of parchment to 0.6 cm/0.25 inch thickness and freeze.
Once firm, cut the filling to the same size as the cookies. Place the filling in between two pieces of the cookies.