Biscuit Top: Mix 250g of the Digestive/Graham biscuit crumbs with 90g of melted butter until it looks like wet sand. Place a piece of parchment paper on top of a chopping board and then place your cheesecake tin (without the tin base) onto the parchment paper and chopping board. Pour the biscuit mixture into the tin, spread and press down firmly until it forms a nice even round base. Carefully lift up the cheesecake tin to reveal the round pressed crust and place into the fridge to set.
Biscuit Base: Mix 500 g Digestive/Graham biscuits, crushed with 180 g unsalted butter, melted until it looks like wet sand. Press firmly into the base of a 23cm x 7cm springform tin. Chill while you make the filling.
Cheesecake filling: In a bowl, mix together the mascarpone cheese, cream cheese, sugar, coffee liqueur, vanilla extract with an electric beater. In a separate bowl, whisk up the heavy cream to medium peak and then fold the whipped cream into the cheesecake mixture
Whipped Cream: In a bowl, whisk together the heavy and sugar until stiff peaks, set aside.
Assemble: Take the biscuit base out of the fridge. Add the cheesecake filling to the bottom of the biscuit base and use a spoon to spread the mixture out evenly. In a separate bowl, mix together the espresso and coffee liqueur. Dip the sponge fingers, one at a time, into the coffee mixture and line them on top of the cheesecake filling. Fill the remaining space of the biscuit base with the whipped cream. Place the biscuit top over the whipped cream to close the pie and place the pie back into the fridge to set for at least 4 hours or overnight.
Serve: Place a chopping board/serving platter on top of the cheesecake and flip it upside down. Release the cheesecake from the springform tin. If you have difficulties unmoulding the pie, use a blow torch to lightly heat up the edges of the springform tin. Slice with a hot, clean knife between cuts for neat slices showing the caramel layer through the middle.