Melt chocolate
Whisk butter, icing sugar and salt.
Add melted chocolate and grated hazelnuts and stir in.
Place in refrigerator for 1 hour or longer.
Roll small balls and put on baking tray with baking paper. Put a whole hazelnut in the middle.
Bake in preheated oven at 160° C for about 13 minutes.
Leave to cool on the baking tray.