1.
Preheat the oven to 180°C and roast the hazelnuts for about 10 minutes until they smell fragrant and the skins split. Watch the nuts carefully so they don't burn.
2.
Remove the hazelnuts from the oven, wrap them in a cloth and rub them to remove the skins. Purée the hazelnuts in a food processor or blender until a fine nut butter forms. This can take 5 minutes or longer. Important: use a powerful blender so the mixture becomes creamy. Do not add water or other liquids, as they will make the butter clump.
3.
Melt the chocolate in a water bath and add it together with the salt to the nut butter. Purée again well.
4.
Fill the spread into sterilized jars and store in the refrigerator. It will firm up there but remain spreadable. If you prefer it runnier, you can soften the spread again in a warm water bath.