1. Roast coriander, cumin, poppy and sesame seeds on a griddle and pound.
2. Roast coconut too. Wash and soak tamarind in 240 ml/1 cup water.
3. Mash well, then squeeze out and discard pulp.
4. Remove stem, slit and deseed chillies without separating them.
5. Pat dry. Heat oil in a kadhai. Fry potatoes till golden brown.
6. Remove. Reserve a few green chillies for garnish.
7. Fry the rest till soft. Drain.
8. In the same oil brown the ginger and garlic pastes, ground seeds, turmeric, chilli powder, curry leaves and coconut.
9. Add green chillies and 480 ml/2 cups water.
10. Cover and simmer for 5 minutes.
11. Add fried potatoes and simmer till chillies and potatoes are tender.
12. Add tamarind juice through a stainer and let simmer till gravy thickens.
13. Garnish with slit green chillies and serve with plain boiled rice.