Process nuts in a food processor for about 5 minutes until you get a smooth liquid butter texture.
Meanwhile melt chocolate over a bain-marie until smooth. Add the melted chocolate, sugar, cocoa powder, oil and vanilla extract to hazelnuts and process until smooth.
Transfer the spread into a small sauce pan and cook at 50 C (very low temperature) for 5 minutes then place finished hazelnut chocolate spread to an airtight container, let cool then refrigerate. Stir before serving.