Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.

In a medium mixing bowl, whisk together the all-purpose flour, baking powder, and salt until well combined.

In a large bowl, cream together the unsalted butter and granulated sugar for 2-3 minutes until light and fluffy.

Beat in the large eggs one at a time, ensuring each is fully incorporated before adding the next, then mix in the vanilla extract.

Dissolve the instant coffee granules in hot water, stirring until completely dissolved. Allow to cool slightly.

Gradually stir the dry ingredients into the butter mixture until just combined.

Drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.

Bake for 10-12 minutes until edges are lightly golden and centers remain soft.

Let cookies cool on the baking sheets for about 5 minutes, then transfer to wire racks.

Beat together mascarpone cheese and heavy cream until smooth. Mix in coffee liqueur if using.

Spread a layer of filling between two cookies to create a sandwich.

Dust with cocoa powder using a fine sieve.