Strip basil leaves from stems, peel avocado and remove the pit.
Add basil, avocado, garlic, hemp seeds, and lemon juice to food processor.
Pulse for 20 seconds until chopped and ingredients combine.
Add oil to form a paste (add more oil by a tablespoon at a time if you want it to be thinner).
Stir in Parmesan cheese.
Top bread with however much pesto you want! Top off with some fresh arugula.
Transfer unused pesto to an airtight container and store in the fridge or the freezer to use later on.