The ONLY pesto recipe you need AND it couldn't be simpler.
If using a blender - Pulse the cashew nuts a few times to roughly crush them before adding the rest of the ingredients and blending until smooth. If the mixture is too thick, add more water a teaspoon at a time until it has reached your desired constancy.
If making by hand - Finely slice the basil and spinach. In a pestle and mortar crush the cashews, garlic and salt with the olive oil and lemon juice. Add in the basil and spinach along with the water and continue to crush until you reach your desired constancy.
If you don't finish all of this off straight away (shock horror!) it can be stored in a glass jar in the fridge for up to three days.