Preheat oven to 350 degrees F
Separate the eggs and put the egg whites in the bowl of your stand mixer. Place the yolks in a separate bowl.
Add the salt to the egg whites and whisk until stiff peaks form.
In separate bowl, mix the butter and Nutella. Once combined, add in the rum, egg yolks, and ground hazelnuts. Finally fold in the melted chocolate
Add one large scoop of the egg whites to the mixture and mix thoroughly. Gently fold in the egg whites a third at a time.
Pour the mixture into the prepared spring-form pan and bake for 40 minutes or until the cake is beginning to pull away from the sides. Let cool on a rack