Pistachios make such great pesto! You'll find all of the traditional ingredients here. Be sure to use enough basil; it may feel like a lot but it processes down. I like to stir in the parmesan when I'm ready to use the pesto in a recipe rather than from the start because sometimes I want pesto with no cheese in it!
In the bowl of a food processor, add the basil, garlic, and salt. Process until the ingredients are finely chopped, stopping to scrape down the bowl a few times as you go.
Add the pistachios and process until they are finely ground, again stopping to scrape down the bowl as you go. You can leave the nuts more coarsely ground if you prefer.
With the processor running, add the oil in a steady stream through the drip hole in the top of the processor. Process until the pesto is glossy and fairly smooth. Stop and scrape down the bowl once or twice.
Transfer the pesto to an airtight container and store in the refrigerator or freezer. When you're ready to use the pesto, stir in the parmesan cheese just before serving.