Preheat your oven to 350°F (175°C). In a mixing bowl, combine crushed chocolate cookies and melted butter until evenly mixed. Press this mixture firmly into the bottom and up the sides of a tart pan.

Bake for 10 minutes until the crust is slightly firm and set. Once baked, remove it from the oven and let it cool completely.

In a large mixing bowl, whisk together mascarpone cheese, powdered sugar, espresso powder, and vanilla extract until smooth and creamy.

Once the crust has cooled, pour the mascarpone filling into the tart shell and spread it evenly.

In a saucepan, combine heavy cream and dark chocolate over low heat. Stir until melted and smooth.

Carefully pour the ganache over the mascarpone filling and spread evenly. Cover and chill in the refrigerator for at least 2 hours.

When ready to serve, slice with a warm knife and garnish as desired.