In a blender add ⅓ cup coriander leaves, ⅓ cup mint leaves, 1 small onion roughly chopped, juice from half a lemon, 1-2 green chillies, ¼ teaspoon chaat masala powder and salt as needed.
Without adding any water, blend all the ingredients together. If the mixture is too dry, add 1-2 tablespoon water and blend into a smooth paste.