The spiciness is up to you. You can use more or less chilies than indicated in the recipe. You can also decide for yourself what kind of chili you want to use.
Roughly cut and discard the stems of coriander and parsley.
Remove seeds from chilies. Discard seeds. Coarsely chop chilies.
Finely puree all ingredients in a blender or with a hand blender.
Season to taste with salt.