In a large mixing bowl, cream the softened butter, brown sugar, and granulated sugar together until light and fluffy, about 2-3 minutes.

Add the eggs one at a time, beating well after each addition. Mix in the mascarpone cheese and vanilla extract until smooth.

In a separate bowl, whisk together the all-purpose flour, cocoa powder, baking powder, espresso powder, and salt.

Gradually fold the dry ingredients into the wet mixture until just combined; the dough will be soft and slightly sticky.

Cover the bowl with plastic wrap and refrigerate the dough for at least 2 hours or overnight.

Scoop out tablespoon-sized portions of dough and roll them into balls, coating them in granulated sugar and then powdered sugar.

Arrange the sugar-coated dough balls on a parchment-lined baking sheet, leaving about 2 inches of space between cookies.

Preheat the oven to 350°F (175°C) and bake the cookies for 10-12 minutes.

Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.

Dust the cooled cookies with a mix of cocoa and espresso powder before serving if desired.