Preheat the oven to 350°F (180°C). Place the nuts on a baking tray and roast them for 6-8 minutes and allow them to cool slightly before processing (note 3). Place the hazelnuts and cashew nuts in your blender or food processor (see note 4 )and begin to blend. Depending on your food processor, it will take 10 to 15 minutes to reach the perfect smooth liquid consistency. If the hazelnuts and cashew nuts stick to the sides, run a spatula alongside the bowl and keep processing. You will feel like nothing is really happening but be patient, and if your food processor is overheating, turn it off for a few minutes and let it cool down. After a while, the magic will start happening – the oil contained in the nuts will break down, and after a few more minutes, you will have smooth nut butter.
While the nuts are processing, break the chocolate into small chunks and place them into a heatproof bowl and melt in the microwave, making sure to check every 15 seconds until melted (note 5).
Once the nut butter is ready and deliciously creamy, add the melted chocolate, the cacao powder, and sugar (or sweetener of your choice, if needed) and blitz for another minute or two.
As soon as it’s ready, it will be quite liquid, as the nuts will be warm. You can put the Nutella in the fridge for up to a couple of hours for a thicker consistency.
Store the Nutella in a sterilized airtight jar and enjoy it. You can keep it a room temperature for around 3 weeks or longer (if it stays around that long)!