Preheat your oven to 325°F (160°C). In a mixing bowl, combine crushed chocolate cookies with melted unsalted butter until moistened. Press into the base of a greased springform pan. Bake for 8-10 minutes, then cool completely.

Beat cream cheese until smooth. Gradually add granulated sugar, mixing well. Add eggs one at a time, then vanilla, sour cream, and cooled espresso. Fold in flour until just combined.

Wrap the springform pan in foil and place in a larger roasting pan. Fill with hot water halfway up the sides. Bake for 60-70 minutes until set. Turn off the oven, leave inside for 1 hour.

Heat heavy cream. Pour over chocolate chips in a bowl and stir until smooth. Mix in a tablespoon of cooled espresso. Pour ganache over cooled cheesecake.

Cover loosely with plastic wrap and refrigerate for 4-6 hours or overnight. Garnish before serving. Slice with a warm, wet knife for neat cuts.