Put all of the ingredients (except the oil) into a food processor.
Blend everything well.
Slow add the oil, while continuing to blend.
Notes
For a brighter green colour, blanch the spinach leaves in boiling water for 30 seconds, then transfer to an ice bath before blending.
Start by pulsing the food processor to break the ingredients up first and then go full speed.
You can chop the spinach up first to make it easier to blend if you prefer.
If your pesto is too thick, add more olive oil or a little water, a tablespoon at a time, until you reach the desired consistency.
For an extra creamy pesto with spinach, try adding a small amount of Greek yogurt or a ripe avocado. This will give your pesto a rich and smooth texture.
You can add some red chilli flakes to the pesto with spinach if you want a kick of heat.
if you don't love the earthy flavour of spinach, then you can cook it in a frying pan for a couple of minutes before stirring it into pasta.