Preheat the oven to 350°F (175°C).
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
Add the eggs, one at a time, and mix well after each addition, then stir in the vanilla extract.
In a separate bowl, combine the flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Chill the dough for at least 30 minutes in the refrigerator.
Roll the dough into 1-inch balls and place them on a baking sheet lined with parchment paper.
Use your thumb (or the back of a spoon) to make an indentation in the center of each ball.
Fill the indentation with chocolate ganache or your choice of filling.
Bake in the preheated oven for 12-15 minutes, or until the cookies are set but still soft.
Allow cookies to cool completely on the baking sheet before transferring to a wire rack.