Blanch the nettles in boiling water for 30 seconds to one minute (you can rinse the nettles off beforehand if you wish, but I'm rather lazy and take my chances). Drain and rinse with cold water. Squeeze the water out of the nettles (you'll be left with maybe 1/2 cup).
Place all ingredients except walnuts in a food processor, blend until smooth. Add walnuts (or other desired nut) and pulse until nuts are in small pieces. Have a spoon handy to relish this wild pesto!