Spread the hazelnuts onto a baking tray and roast them for 15 minutes.
Remove the hazelnuts from the oven and place them into a food processor. Blend on high until you have a thick and creamy nut butter.
Break the dark chocolate into chunks and melt with the coconut oil in the microwave, or over a low heat on the stove.
Add the melted chocolate mixture to the blender, along with the maple syrup, milk, vanilla extract, and salt. Blend again for a few minutes until the mixture is smooth.
Transfer to a sterilized jar, and store at room temperature or in the fridge (if you like the thicker texture). It will last well for a month.