Heat kadai with oil. Add mustard, splutter and add urad dal followed by curry leaves. Transfer to serving boil.
Add the coriander leaves in same kadai and saute in low flame only till the leaves gets reduced in volume and without changing the colour. (The leaves should be with water, or else the leaves will get browned and will give different smell).
Take a mixer. Add coconut, roasted gram dal (pottukadalai), ginger, tamarind, turmeric, salt, chilli and sautéed leaves.
First grind without water and then add water and grind smoothly.
Transfer to the serving bowl with tadka, mix well.