Place all the ingredients, but just 60 ml (¼ cup) of the olive oil, into a blender or food processor and blend.
Using a spatula, scrape the sides of the blender or food processor to ensure everything blends together smoothly.
Add the additional 40 ml (about 3 tbsp) of olive oil, as needed, until the pesto is smooth.
Taste and adjust the seasoning.
Transfer to an airtight container, cover with more olive oil to prevent oxidizing, and enjoy. See recipe tips for more info on storing in the fridge and freezer.