Grease and line a 23x23cm square cake tin.
Combine the base ingredients and press into the lined tin.
Bake for 8-10 minutes until golden.
Cool before topping.
Blend the cashews, blackcurrant purée, vanilla and xylitol on high speed in a powerful blender until completely smooth, scraping down the sides halfway through to make sure there are no lumps remaining. Be careful not to add too much extra water, just enough for the mixture to blend properly.
With the blender still running, stream in the cocoa butter and blend until fully incorporated.
Fold through the blackcurrants and spread evenly over the cheesecake base.
Freeze until firm.
Cut into 8 fingers and decorate with fresh berries.