Toast the hazelnuts in a pan on medium-high heat for 3-4 minutes, stirring continuously to evenly distribute the heat.
Melt the dark chocolate either in a double boiler or in the microwave. Stir every 30 seconds to distribute the heat if using the microwave.
Add the warm hazelnuts to a food processor and start the machine. Process the hazelnuts until they turn into a paste and release their oil. This may take up to 15 minutes. Stop the food processor from time to time to scrape the sides of the bowl and to prevent the machine from overheating.
When the hazelnuts have turned into a paste, mix in the powdered sugar and then pour in the oil while processing.
Add the cocoa powder and mix to incorporate.
Lastly, pour in the melted chocolate. Give it a final blitz to incorporate.
Transfer the mixture to a jar and let set in the fridge for 1 hour.
Notes
Store at room temperature for best spreadabilty. This hazelnut spread is made with shelf-stable ingredients that do not require refrigerating.Room temperature can play a major role as this homemade chocolate spread is quite sensitive and may be much softer in a hotter climate and not so spreadable in a colder one. Some chilling will firm up a runny spread, while some quick microwaving will make a hard homemade nutella spreadable.Dark chocolate comes at various percentages of cocoa. The higher the cocoa percent, the lower the cocoa butter. More cocoa butter in your chocolate of choice will provide extra creaminess, which will lack, instead, if using a very dark chocolate with a high cocoa percent.