Preheat your oven to 180ºC (355ºF). Melt butter in a saucepan over low heat and let it cool to room temperature. In a large bowl, combine melted butter with granulated and dark brown sugar until creamy—about 1 minute.

Add in one large egg and a teaspoon of vanilla extract. Mix until fully incorporated and creamy.

In a separate bowl, whisk together all-purpose flour, baking powder, baking soda, instant espresso powder, and salt. Gradually fold this into your wet ingredients until just combined.

Use a 2-tablespoon cookie scoop to portion out the dough, roll into balls, and place on a parchment-lined baking sheet. Chill for 30 minutes.

Bake in the preheated oven for 10-11 minutes, until the edges are lightly golden and the centers remain soft. Let cool on the baking tray for about 3 minutes.

In a medium bowl, combine mascarpone cheese, vanilla extract, confectioners sugar, agave or honey, and heavy cream. Whip until stiff peaks form.

Once cookies have cooled, pipe a generous dollop of the mascarpone cream on each cookie and dust with cocoa powder.