Melt the cacao butter in a double boiler – fill a small saucepan and bring it to the boil, and turn down to a very low simmer. Place a ceramic or glass bowl on top (if you don’t have an actual double boiler) and melt the cacao butter until liquid.
Add all ingredients except whole hazelnuts into food processor and process until thoroughly combined. Decant mixture into a bowl and stir the whole hazelnuts through. Scrape all of the mixture onto a tray lined with baking paper. It should be roughly an inch deep.
Place in the fridge to set, and cut into pieces as desired (I think the smaller the better).