Start by preheating your oven to 350°F (175°C) and lining a baking sheet with parchment paper. In a bowl, whisk together the all-purpose flour, instant espresso powder, baking powder, baking soda, and salt. In a separate large bowl, beat the softened unsalted butter with granulated and brown sugars until light and fluffy. Add the egg and vanilla extract, mixing until combined. Gradually incorporate the dry ingredients into the wet mixture, stirring until just combined. The dough will be slightly sticky.

Using a 4-tablespoon cookie scooper, portion out the dough onto the prepared baking sheet, spacing them about 2 inches apart. Bake in the preheated oven for 10-12 minutes, or until the edges are golden and the centers have set. Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.

While the cookies are cooling, prepare the mascarpone cream. In a medium bowl, beat the mascarpone cheese until smooth. Add the whipping cream and powdered sugar, continuing to beat until the mixture is thick and spreadable, resembling buttercream frosting. Be careful not to overwhip, as this can cause the cream to become too stiff.

Once the cookies have cooled, spread a generous layer of the mascarpone cream on top of each cookie using an offset spatula. Lightly dust the tops with cocoa powder using a fine mesh sieve. For a slightly different dessert twist, you can try layering flavors similar to the Boston Cream Pie Cookies Recipe. Serve immediately or refrigerate until ready to serve.