In a food processor, process biscuits until crumbs are formed. Add melted butter and process again until combined. press into bottom of 8-inch (20-21 cm) springform pan. Refrigerate while making the filling.
In a large mixing bowl beat cream cheese and powdered sugar. Beat until smooth and creamy. Add Nutella, cocoa powder and vanilla extract. beat again until smooth and creamy.
Pour the cheesecake mixture into the springform pan. Refrigerate for at least 6 hours or overnight. You can also freeze the cake.
Prepare the ganache: place the Nutella in a large bowl and set aside. in a small saucepan bring heavy cream to a simmer, remove from heat and pour over the Nutella. Let stand 1-2 minutes and stir until ganache is smooth.
Let cool slightly and pour over the cheesecake. You can pour straight into the springform pan or open it and then pour the ganache.
Freeze for two hours before serving.
For Aesthetic look, before you remove the springform pan, run a knife around the outer edge of the cheesecake to loosen it from the pan. Then remove the sides of the springform pan.