To make the herb oil, blend together all ingredients in a food processor or blender, and strain through a fine mesh sieve. Store in the fridge for up to three days.
Notes
This also makes a delicious pesto. If you want a pesto instead, don’t strain it. The stems of cilantro give off a lot of heat. If you want more heat in this, you can add some stems to the blender and some chili pepper flakes.