In the bowl of a food processor add the cake and blitz until crumbs. Add the melted dark chocolate into the mixture and pulse to combine.
Remove the cake dough from the food processor and press into a greased and lined 18cm deep cake tin, with a removable base.
Place into the fridge for 1 hour.
To make the cheesecake filling, combine the cream cheese, mascarpone and sugar in a large bowl and then add the double cream, whisking until slightly thickened. Add the melted white chocolate and vanilla extract and stir to combine then spoon into the cake crust. Spread the mixture out and smooth the top with a palette knife or the back of a spoon, then place into the fridge for at least 3 hours, or until set.
To make the glaze, place the chocolate, butter, and cream in a heatproof bowl and place over a bowl of simmering water. Stir occasionally until melted then remove from the heat and allow to cool slightly. Pour the chocolate glaze over the cheesecake, spreading it out to the sides. Chill just until the chocolate has just set - about 10 minutes - then serve in slices.