Add pine nuts, garlic and parmesan cheese to a food processor and pulse several times. Scrape down the sides of the bowl. Add basil and pulse until well chopped. Scrape down the sides of the bowl.

Add lemon juice and then slowly drizzle in the olive oil, as you pulse. Start with 1/2 cup. Add salt and pepper, to taste. Add more olive oil, until it reaches a soft sauce consistency.

Store immediately in an airtight container, in the fridge, until ready to use. If storing for more than a day, pour a thin layer of olive oil on top of the pesto to help prevent oxidation (turning brown).