I usually prefer roasting some jeera (cumin seeds) and storing it in airtight container and use it when ever needed for chaas, raitas, stir fries.
But you can just dry roast 1 teaspoon of jeera and use it here in this recipe.
You can either powder it in hand mortar and pestle or just grind it in the mixer along with chillies.
I powdered in mixer as I did little more than needed to store and use.
Deseed the chillies and chop roughly.
Blend curd, chillies, jeera powder, coriander leaves, salt well, until its frothy.
You can add black salt while blending or for garnishing too. I used for garnishing. (I changed the mixer as the one I used gone faulty in between, so u may find two blenders)