Preheat your oven to 350°F (175°C).
Cream the softened butter and granulated sugar together.
Add in the egg and vanilla extract; beat well.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients into the wet mixture, mixing until just combined.
Fold in the chocolate chips gently.
Scoop the dough into equal-sized balls and place them on a lined baking sheet.
With your thumb, create an indentation in the center of each ball of dough.
Bake for 12-15 minutes until the edges are set but the centers remain moist.
Remove from the oven and let cool for a few minutes before transferring to a wire rack.
Fill each thumbprint with chocolate filling or jam of your choice.
