Roast the onions till it has a bot of char and keep aside and repeat with the coconut and green chilli
In a food processor, add the onion and chilli, followed by the coconut, ginger and garlic, peppercorns and cinnamon
Add water and grind till smooth
Strain this through a sieve and use additional water to keep grinding and straining to reserve the smooth liquid
In a saute pot add the oil and allow it to heat
Add the chicken in a layer so it can get some color on both sides
Add 2 tbsps of the 3 tbsps of East Indian masala and cook for 10 mins
Remove and keep aside
In the same oil, saute the ground masala for 5 mins to cook off any raw taste
Add the chicken back in, add the tamarind paste and salt to taste
Add the water and cook covered for 10 - 15 mins
Add salt to taste, the last tbsp of East Indian masala, stir
Add the potatoes and cook for 5 - 7 mins
Garnish with coriander