Line the base of a 20cm/8-inch springform pan with baking parchment. Crush the digestive biscuits into fine, even crumbs, then stir them into the melted butter until thoroughly coated.

Press the biscuit mixture firmly into the prepared pan, using the bottom of a glass or measuring cup to create a compact, level layer. Refrigerate the base while you prepare the filling.

Beat the slightly softened cream cheese, room-temperature Nutella, sifted icing sugar, and vanilla extract until smooth and fully combined. Stop mixing as soon as the mixture is creamy to avoid overbeating.

Whip the cold double cream in a separate bowl to soft or medium peaks. Fold it gently into the Nutella mixture in batches until no pale streaks remain.

Spoon the filling over the chilled biscuit base and smooth the surface with a spatula. Cover the pan and refrigerate for at least 6 hours, preferably overnight.

Remove the cheesecake from the pan while it is cold. If needed, briefly warm the outside of the springform pan with a warm towel before unclipping it, then decorate with whipped cream, warmed Nutella, and chopped hazelnuts.