Lightly grease a 9 inch springform pan with cooking spray and set aside.
Crush the biscuits by hand or in a food processor until you get fine crumbs. Add the chopped hazelnuts, the melted butter and chocolate to the crumbs and mix together. Press down the mixture into the pan. Place in the fridge.
In a large bowl, cream together the cream cheese, icing sugar, Nutella and the crushed Ferrero Rocher. Set aside.
Whip the heavy cream and fold it gently in the cream cheese mixture.
Pour the mixture into the pan over the biscuit base.
Place in the fridge overnight or in the freezer for about 6 hours.
Once the cheesecake is set, remove from the springform pan. Decorate with melted chocolate, crushed nuts, and Ferrero Rocher chocolates.