Begin by melting the butter in a microwave-safe bowl, then allow it to cool to room temperature. In a large mixing bowl, combine the melted butter with granulated and brown sugars, whisking for about 1 minute until smooth and creamy. Next, add in the egg and vanilla extract, mixing until fully incorporated.

In a separate bowl, whisk together all-purpose flour, baking powder, baking soda, instant espresso powder, and salt until evenly blended. Gradually add this dry mixture to the wet ingredients, stirring gently until just combined to create the dough for the Tiramisu Cookies.

Using a cookie scoop, portion out 11 equal cookie balls and roll them gently in your hands to form smooth balls. Place the cookie dough balls on a plate and chill them in the refrigerator for 30 minutes.

While the cookie dough is chilling, preheat your oven to 180ºC (355ºF). Line a baking sheet with parchment paper to prevent sticking.

After chilling, arrange 6 cookie dough balls on the prepared baking sheet, leaving enough space for spreading. Place the tray in the oven and bake for 10-11 minutes, or until the edges look set. Let the cookies cool on the tray before transferring them to a wire rack.

In a medium bowl, combine mascarpone cheese, vanilla extract, confectioners sugar, agave, and heavy cream. Whip the mixture until stiff peaks form, usually taking about 3-5 minutes.

Once the cookies are completely cooled, pipe a generous layer of the mascarpone cream on top of each cookie. Dust a light layer of cocoa powder over the cream.