Measure 5 tbsp cold water in a small bowl, then sprinkle over the gelatine and leave to soak for 5 mins until spongy. Now stand the bowl of gelatine in a pan of gently simmering water and leave until it turns clear.
Meanwhile, mix the biscuit crumbs and butter really well, then press on the base of a loose-bottomed 20cm cake tin. Chill.
Beat the quark, mascarpone and Baileys together, then stir in the gelatine and fold in the cream.
Whisk the eggs and sugar in a bowl until thick, pale and foamy, then fold into the cheesecake mixture and pour onto the biscuit base. Chill for 3-4 hrs or until set.
For the jelly, sprinkle the gelatine over the coffee, then put the bowl in a pan of gently simmering water until dissolved. Cool the mixture. When cold, carefully spoon the coffee mixture on top of the cheesecake to make a thin layer – don’t pour it on or you will disturb the creamy layer. Chill until set. Will keep in the fridge for 2 days.
To serve the cheesecake, wrap a hot tea towel round the outside of the tin, then gently ease out the cake. Serve in thin slices.