Preheat your oven to 170 degrees (fan) and place hazelnuts in a single layer on a rimmed baking sheet
Roast on the middle position of your oven rack for 10–12 minutes. You’ll know they’re ready when they’re fragrant and lightly golden.
While still warm, wrap the hazelnuts in a clean kitchen towel, tea towel, or dish towel and rub them together to remove the hazelnut skins (don’t worry about the skins as a little bit left is fine)
Place hazelnuts into a high speed blender or food processor. Blend for a few minutes, scraping down the sides of the bowl as needed.
At first, it will look like a dry paste, but give it a bit of time as the natural oils will release and turn it into smooth hazelnut butter.
Melt your chocolate in the microwave in 30 second bursts and let it cool slightly to room temperature.
Slowly pour the creamy nut mixture into the melted chocolate while stirring.
