Prepare the ingredients:
Rinse and pat dry the basil leaves. Peel the garlic cloves.
Blend the dry ingredients:
In a food processor or blender, combine the basil leaves, Parmesan cheese, pine nuts, and garlic. Pulse until the mixture is finely chopped.
Add the olive oil:
With the processor running, slowly drizzle in the olive oil. Blend until smooth, scraping down the sides with a spatula as needed.
Season:
Stir in the salt and black pepper. Taste and adjust seasoning as desired.
Store or serve:
Transfer the pesto to an airtight container. If storing, drizzle a thin layer of olive oil on top to prevent browning. Use immediately or refrigerate for up to 1 week.