Preheat the oven to 180°C.
In a bowl, mix the crushed digestive biscuits with the melted butter. Press the mixture into the base of a greased 9-inch springform tin and chill in the fridge.
In a saucepan, stew the rhubarb with the caster sugar and ground ginger until soft. Leave to cool.
In a separate bowl, beat together the mascarpone cheese, icing sugar, lemon zest, and double cream until smooth.
Swirl the stewed rhubarb through the cheesecake mixture, then pour over the biscuit base.
Bake in the oven for 40-45 minutes until set. Allow to cool completely before serving.
