Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Cream together softened unsalted butter and granulated sugar using an electric mixer on medium speed for about 2-3 minutes.

Dissolve the espresso powder in hot water and add it to the butter and sugar mixture along with the eggs and vanilla extract. Beat until smooth.

Whisk together the flour, baking powder, and salt in a separate bowl, then fold into the wet ingredients carefully.

Fold in the mascarpone cheese until just combined, ensuring no large lumps remain.

Scoop the dough into balls and place them about 2 inches apart on the prepared baking sheet.

Bake for 10-12 minutes until the edges are golden and centers are slightly set.

Cool on the baking sheet for 5 minutes before moving to a wire rack.

Dust cooled cookies lightly with cocoa powder before serving.