Start by toasting the hazelnuts in a hot pan (or 5-10 minutes in the oven at 200 degrees Celsius (392 degrees Fahrenheit)) until they get a bit of color. Then rub the skins off the nuts and let them cool.
Use a mini chopper to blend them until you get hazelnut flour.
Coarsely chop the chocolate and place it in a bowl.
Carefully heat the cream in a heavy-bottomed saucepan and when it boils, pour it over the chocolate in the bowl.
Stir well to ensure all the chocolate is melted. Then cut the butter into smaller pieces and add it.
Stir well until the chocolate and butter are melted together and the mixture is smooth and glossy.
Finally, stir in the hazelnut flour and salt.
Scald a glass jar with a lid and pour the Nutella in while it's still warm.
Make sure to take it out of the fridge a bit before serving as it can be a little difficult to spread on your bread otherwise.