To make the base, blitz the biscuits, butter and Nutella in a food processor until it starts to clump. Add the hazelnuts and salt and pulse until you have a damp, sandy mixture.
Pour into a round, greased 23cm (9.5 inch) springform tin and press into the base using your hands. Refrigerate.
To make the filling, put the cream cheese and icing sugar in a stand mixer and beat until smooth.
Add three quarters of the Nutella and the salt and continue to beat until combined. Gently fold in the remaining Nutella by hand in order to "swirl" it in, so it isn't entirely incorporated.
Take the base out of the fridge and pour the Nutella mixture over it, carefully smoothing out the top.
Refrigerate for at least 4 hour or overnight before cutting. Serves 8.
Happy baking!
Recipe by Butter Baking at https://www.butterbaking.com/2012/10/20/nutella-cheesecake/