In a large mixing bowl, cream together the unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes. Beat in the eggs one at a time.

Stir in a splash of vanilla extract for extra flavor. Gradually add the all-purpose flour, espresso powder, and salt until just combined.

Cover the bowl with plastic wrap and refrigerate for at least 30 minutes.

Preheat your oven to 175°C (350°F) while the dough chills.

Remove the dough from the refrigerator, scoop portions, and roll into balls. Coat them with powdered sugar.

Arrange the balls on a lined baking sheet, spaced apart.

Bake for 10-12 minutes until edges are set and tops crack.

Cool briefly on the baking sheet before transferring to a wire rack.

While warm, gently press the center of each cookie to create a well.

In a mixing bowl, combine mascarpone, heavy cream, and powdered sugar, whipping until glossy and smooth.

Fill each well with the mascarpone mixture and lightly dust with cocoa powder.

Chill in the refrigerator for about 15-20 minutes before serving.