1/2tspsaltor more salt to taste if you skip the parmesan
Instructions
In a food processor, combine the arugula, garlic, olive oil, walnuts, and parmesan cheese (if using). Process the ingredients until a smooth pesto forms. You will need to scrape down the sides a few times with a rubber spatula.
Taste the pesto and add salt if needed. If you include parmesan, you may not need any additional salt.
Refrigerate for up to 4 days or freeze for several months. I recommend freezing the pesto in an ice cube tray and then storing the cubes in an airtight container. That way, you can take out a small amount for a sandwich or snack whenever you need it.