"Put these weeds to good use in a sauce that's bursting with so many vitamins and minerals, it could be called a Spring Tonic. It's a perfect complement to mild fish like halibut, grilled chicken, and it gives your minestrone another interesting layer of flavor."
Place hazelnuts in a dry skillet over medium heat; cook and stir until toasted, 3 to 4 minutes.
Bring a pot of water to a boil. Wearing gloves, add nettles to boiling water; cook until nettles are tender and still maintain the bright green color, about 2 minutes. Immediately transfer to a colander and run under cold water to stop the cooking process. Let nettles cool and drain.
Place the nettles in a clean kitchen towel and squeeze excess water from the greens.
Combine nettles, hazelnuts, Parmesan cheese, and salt in a food processor fitted with a puree blade. Pulse a few times before turning the processor on. Stream olive oil through the feeding tube while the processor is running until pesto is smooth.