Preheat the oven to 180°C and put a pan of water in the oven. Line a 22 cm springform tin with baking paper and grease the paper.
Crust: Mix the biscuits and melted butter and stir in the liqueur. Press the crust onto the bottom of the prepared tin.
Filling: Beat the cream cheese, mascarpone cheese and sugar until smooth. Mix in the liqueur and coffee granules. Slowly stir in the eggs and flour until just blended.
Turn the mixture into the prepared crust and bake for 40-45 minutes or until just set.
Open the oven door, switch off the oven and leave the cake to cool in the oven for 20 minutes. Remove and leave to cool completely.
Chill in the fridge for at least three hours before serving.
Topping: Heat the chocolate pieces, cream and coffee, stirring until the chocolate has just melted. Drizzle over the cake in a zigzag pattern.