Toast 1½ cups hazelnuts in a cast iron skillet. Roll in a pillowcase or dishtowel to remove most of the dark skin (if the skin is stubborn, you didn't roast enough—return to the skillet). Place in food processor.
Process until hazelnut pieces are coffee-ground sized but still powdery. Remove ½ cup or so for hazelnut coffee; store in airtight container in refrigerator.
Add 1½ cups toasted sunflower seeds, 1 cup dark chocolate chips and ½ tsp salt to food processor. Process until it forms into a ball. Store in airtight container. I expect this to keep as long as any other preservative-free nut butter. Originally I stored my nut butter in the fridge, but the next morning it was too stiff to spread well. It's clearly much better to store it at room temperature, as long as it's used up quickly.
This butter is not as smooth, oily, or sweet as the commercial product you may be thinking of; it's more like Justin's Chocolate Hazelnut Butter.
Both recipes will benefit from some tweaking to your own personal preference, but as a proof of concept both of these ideas are obvious winners.