Heat a small pan over medium-high heat. Toast the pine nuts until light golden brown, watching closely to prevent burning. Remove immediately.
In a food processor, combine the basil, Parmesan, garlic, salt, and pepper. Pulse until finely chopped.
With the machine running, slowly drizzle in the olive oil until the sauce is smooth and glossy.
If too thick, add a tiny splash of water or a little more oil to reach desired consistency.
Notes
Store in an airtight container in the fridge for up to 3 days. To prevent oxidation (browning), press a thin layer of olive oil over the top. Can be frozen in ice cube trays for up to 3 months.