Bring a large pot of salted water to boil. Add spaghetti and cook until al dente. Drain water.
In a food processor, puree together pistachios, basil, garlic, salt, and ½ cup olive oil until smooth. Add in Parmesan and pulse. If the mixture is too thick, add in a little olive oil at a time until it reaches the right consistency.
Once pasta is cooked, combine with pesto. Garnish with basil and serve immediately.
Recipe by Things I Made Today at https://www.thingsimadetoday.com/2014/10/01/sicilian-pistachio-pesto-pasta-sicily-vacation-recap/