Preheat your oven
Preheat the oven to 180°C / 350°F. Bake the hazelnuts 8 - 10 minutes in a baking tray, lined with parchment paper.
Remove the skin from the hazelnuts and blend into a paste.TipBlend for a few minutes until the paste is silky and oily.
Sit the heatproof bowl over a pan of barely simmering water (a bain marie) and allow the chocolate to melt, stirring occasionally.
Mix the chocolate into the paste, add the icing sugar, pinch of salt, hazelnut oil and unsweetened cacao. Blitz and let cool in a jar.