Preheat your oven to 150°C / 300°F.
Spread the hazelnuts in a single layer on a baking sheet. Place them int the pre-heated oven, and toast for 20-30 minutes, until fragrant and the skin is starting to crack. Watch them carefully to avoid from burning.
Remove the nuts from the oven and let cool slightly.
Place the nuts in an old kitchen towel, and rub to remove the skin. You may need to do this in batches, or stop and pick out those that are skinned and then do a second round with those that aren't. I never get all of the skins off, and I never stress about it.
Pit the dates and place in a small pot together with the oat milk.
Place the pot on medium high heat. Once the oat milk starts to bubble, turn the heat off and place a lid on the pot to soften the dates.
Place the hazelnuts in a food processor, pulse a few times, and then process until a completely smooth hazelnut butter forms - you may need to scrape down the sides a couple of times. How long this takes will depend on how powerful your food processor is, and how old your nuts are. In my food processor I have hazelnut butter in about five minutes.
Add the coconut oil, cocoa powder, dates along with all of the oat milk, salt, and vanilla. Process until smooth.
Transfer the chocolate hazelnut spread into clean airtight glass jars.