Step 1 Heat the oven to 400 degrees. Spread the hazelnuts evenly over a cookie sheet and roast until they darken and become aromatic, about 10 minutes. Transfer the hazelnuts to a damp towel and rub to remove the skins.
Step 2 In a food processor, grind the hazelnuts to a smooth butter, scraping the sides as needed so they process evenly, about 5 minutes.
Step 3Add the cocoa, sugar, vanilla, salt and oil to the food processor and continue to process until well blended, about 1 minute. The finished spread should have the consistency of creamy peanut butter; if it is too dry, process in a little extra hazelnut oil until the desired consistency is achieved. Remove to a container, cover and refrigerate until needed. Allow the spread to come to room temperature before using, as it thickens considerably when refrigerated. It will keep for at least a week.