In a mixing bowl, whisk together all-purpose flour, granulated sugar, baking powder, and salt. Cream unsalted butter until smooth, then add in eggs and the espresso powder, mixing until fully combined. Cover and chill for about 30 minutes.

Preheat your oven to 175°C (350°F) and line a baking sheet with parchment paper. Roll the chilled dough into 1-inch balls, then roll in powdered sugar until coated. Place on the baking sheet, spaced apart.

Bake for approximately 10-12 minutes until lightly golden on the edges. Remove and create an indent in the center of each cookie.

Allow to cool before transferring to a wire rack.

Prepare the creamy filling by whipping mascarpone cheese and heavy cream until glossy and thick, about 2-3 minutes.

Once cooled, fill each crater of the cookies with the mascarpone mixture and dust with cocoa powder.

Chill filled cookies for 15-20 minutes if desired. Store unfilled cookies at room temperature and filled cookies in the fridge for up to 2 days.