Make the cheesecake base: melt the butter in a small pan over a medium heat. Blitz the biscuits in a food processor to a fine crumb, add the melted butter and pulse until well combined. Tip into a 23cm springform cake tin and press down firmly into the base. Chill while you make the filling.
Beat the cream cheese and icing sugar in a bowl to soften. Whisk the cream and vanilla in a separate bowl until soft peaks form, then fold into the cream cheese. Stir through the chopped chocolates. Spoon over the biscuit base and smooth with a spatula. Cover with cling film and chill for at least 6 hrs, or overnight.
Once it has set, place the chocolate hazelnut spread in a saucepan and melt over a low heat for 3-4 mins until runny. allow to cool slightly before spreading over the top of the cheesecake. Decorate with remaining chocolates and some chopped hazelnuts. Chill until ready to serve.