Wash the basil leaves thoroughly and pat them dry.
In a food processor, combine the basil, garlic, and pine nuts.
Pulse the mixture until finely chopped.
Scrape down the sides of the bowl as needed.
Add the grated Parmesan cheese to the mixture.
With the food processor running, slowly drizzle in the olive oil.
Blend until the pesto reaches your desired consistency.
Season with salt and pepper to taste.
If the pesto is too thick, add a little more olive oil or water.
Transfer the pesto to an airtight container for storage.