Place parsley, arugula, pine nuts, parmesan cheese, and garlic cloves into the bowl of a food processor. Pulse to incorporate. Then, running the motor, stream in the olive oil.

Stop the motor, scrape the walls of the bowl and pulse again, until everything is well-incorporated. Add salt and pepper and pulse to incorporate. Taste and adjust spices, if necessary.

When the pesto is processed to your liking, scrape it into a mason jar. For best refrigerator life, cover the top of the pesto with a thin layer of olive oil. When you go to remove pesto from the jar, make sure to use a clean spoon and refresh the olive oil layer.