Soak the nuts overnight in cold water.
Pour the boiling water over the dates, leave to absorb for 10 mins., drain well. Blitz the rolled oats and hazelnuts in a food processor, add the dates and cinnamon, then puree. Transfer the mixture to the prepared tin, press down flat. Refrigerate the base until needed.
Drain the cashew nuts, puree the nuts in a food processor/blender along with all the other ingredients up to and including the water. Spread half of the filling over the base, smooth down. Top with 50 g of blueberries. Puree the remainder of the filling with 250 g of blueberries, transfer to the tin and smooth down. Top with the remaining 50 g of blueberries. Place the tin in the freezer for at least 6 hrs.
Allow the cheesecake to thaw out for approx. 30 mins. prior to serving.