spread in a pan and toast the hazelnuts until they're slightly browned and the skin is slightly blistered, 10-15 minutes.
Place the hazelnuts in a cloth towel and rub vigorously to remove as much of the skins as you can, let cool
Place the chocolate in a double broiler (in a clean dry metal bowl over a saucepan of boiling water - don't let the bowl touch the water) until melted and smooth, put aside and let cool
in a food processor (or high powered blender) grind the hazelnuts until they form a nut butter, it will take 6-10 mins depending on the strength of your processor, scraping the sides occationally
Add the powdered sugar, vanilla, cocoa and salt and continue to mix until the mixture is as smooth as possible
add the melted chocolate and blend until smooth
store in an airtight container at room tempurature for up to 2 weeks