Wash the brinjal and dry well using a kitchen towel. Carefully slit four ways only till the middle.
Shallow fry the brinjals in oil on medium flame till golden brown. Fry the brinjal immediately after slitting them else they would turn black.
Sauté 3 roughly chopped onion in some oil on medium flame till nice and brown.
Cool the onions and grind with 2 tablespoons of water to a fine paste
For the main masala, dry roast separately all the above mentioned ingredients (masala paste) on low flame till it slightly changes colour and you get an aroma. Cool the ingredients.
Grind the masala ingredients in a mixer to a smooth paste. Add some water only after grinding the ingredients dry initially, else the masala would not be ground smooth.
Pound garlic, ginger, half green chilli, a pinch of salt and few leaves of coriander in pestle and mortar to make a fine paste.
In a kadai, heat 5 tablespoons oil, add the freshly minced ginger garlic paste, few curry leaves, 1 slit green chilli and add the onion paste. Sauté for 2 minutes.
Now add one finely chopped tomato and also the pulp extracted from the soaked tamarind. Let it come to a gentle boil. Later add asafoetida, turmeric powder, Kashmiri red chilli powder, dhaniya powder and some salt and cook till the oil separates.
Next add the ground masala and around 1 cup water and cook again till the oil separates.
Next add the shallow fried brinjals and cover and cook for around 8 to 10 minutes on a medium flame. Keep stirring in between as the nutty mixture tends to settle at bottom. Also add water if required. Cook till you see oil floating on top.
Finally garnish with fresh chopped coriander.