Adapted from America’s Test Kitchen!
Yield: 1 1/2 c.
8 oz. Hazelnuts (about 2 cups)
4 oz. Confectioners' sugar (about 1 cup)
1 oz. Cocoa powder (about 1/3 cup)
1 fl. oz. Hazelnut, walnut, or vegetable oil
1 tsp. Vanilla extract
1 tsp. salt
Adjust oven rack to middle position and heat oven to 375º F. Place hazelnuts in single layer on rimmed baking sheet and roast until fragrant and dark brown, 12 to 15 minutes, rotating baking sheet halfway through roasting.
Transfer hazelnuts to medium bowl. When hazelnuts are cool enough to handle, place second medium bowl on top shake vigorously to remove skins.
Process peeled hazelnuts in food processor until their oil is released and they form a smooth, loose paste, about 5 minutes, scraping down bowl often.
Add sugar, cocoa powder, oil, vanilla, and salt and process until fully incorporated and mixture begins to loosen slightly and becomes glossy, about 2 minutes, scraping down the bowl as needed.
Transfer spread to jar with tight-fitting lid. Chocolate-hazelnut spread can be stored at room temperature or refrigerated for up to 1 month.