Preheat the oven to 180°C.

Place the hazelnuts on a baking tray lined with baking paper and roast for 7-8 minutes. Let them cool completely. Place the hazelnuts in a food processor and pulse on high speed for about 3-4 minutes, until you get a thick nut paste. Scrape the sides of the bowl, add the remaining ingredients, and continue pulsing on medium speed for 5-6 minutes until you have a smooth butter.

You can keep it in the fridge for up to 1 week.