Preheat your oven to 350°F (175°C).
In a mixing bowl, whisk together the flour, cocoa powder, baking soda, and salt.
In a separate bowl, cream the softened butter with granulated and brown sugar until light and fluffy.
Add the egg and vanilla extract to the creamed mixture, beating until well combined.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Scoop the dough into a greased muffin tin, pressing it into the base and sides to create cups.
Bake for 10-12 minutes or until the edges are set but the centers are slightly soft.
Remove the cookie cups from the oven and let them cool in the pan for about 5 minutes before transferring them to a wire rack.
In a clean bowl, whip heavy cream until stiff peaks form.
Gently fold in the mascarpone cheese, cooled coffee, and powdered sugar until well combined.
Carefully spoon or pipe the mascarpone filling into the cooled cookie cups.
Garnish the filled cookie cups with shaved chocolate.
Refrigerate the cookie cups for at least 30 minutes before serving.
