Place the peanuts in the food processor and let it run for 3-4 minutes. You will see the peanuts transform from crumbs to a dry ball to a creamy peanut butter.
At this point add the chopped dark chocolate and a pinch of salt. You could also add sugar or maple syrup if you wish. Run the food processor again until the dark chocolate pieces melt and completely integrate with the peanut butter.
Keep in a glass jar in the fridge. It will keep good for several weeks.