In a kadai, add a tsp of oil and saute the ingredients(coriander seeds, channa dhal, urad dhal, red chilli, a portion of shallots, coconut) for grinding. Saute until they turn golden brown in colour.
Allow it to cool and grind it to a smooth paste with little quanity of water.
Soak the shallots in water for 2 hours. It helps in peeling the skin easily. Next day peel the skin and chop them if they are big.
Pressure cook the potatoes, peel off the skin and chop them into big chunks.
Boil the tamarind in water and extract tamarind juice.
In a kadai, add gingelly oil and splutter mustard seeds. Once they splutter add curry leaves, green chillies and saute.
Add the remaining shallots and saute until they become transparent.
After the shallots become transparent, add the tomatoes, cooked potatoes.
To this add extracted tamarind juice, turmeric powder, salt and jaggery.
Then add the ground paste and allow to boil.
Cook in medium flame for five more minutes.
Garnish with coriander and serve with rice.