Prepare Basil: Rinse the basil leaves in cold water and gently pat them dry with paper towels.
Blend Ingredients: In a food processor or blender, combine the basil leaves, garlic, and pine nuts. Pulse a few times until chopped. You can also use a mortar and pestle for a more traditional approach.
Add Cheese: Add the grated cheese to the mixture and pulse again until mixed.
Mix in Olive Oil: While the food processor is running, slowly pour in the olive oil in a steady small stream. This will help to emulsify and blend the oil into the mixture. Scrape down the sides of the food processor as needed.
Season: Once the mixture is a smooth paste, transfer it to a bowl. Taste and season with salt and pepper as needed.
Storage: If you're not using the pesto immediately, store it in an airtight container in the refrigerator. It can be stored for up to a week. To preserve its bright green color, you can place a layer of olive oil on top of the pesto.