Place all ingredients in a food processor and pulse until everything comes together and has been well blended. If you want a smoother pesto then simply process until you have the desired texture.
Season with salt once you have processed the pesto as Parmesan cheese does increase the salt content.
Notes
If you want to thin your pesto out simply add more olive oil, tablespoon at a time, until you get the desired consistency. Store in the fridge for up to 5 days. Recipe is also suitable to freeze.