Wash and pat dry brinjal. Slice into thin, long strips. Rub 1/2 tsp salt and 1/4 tsp turmeric and keep aside for 10 min in a bowl.
Soak tamarind in 1/2 cup of water and keep aside.
Place a small pan on flame, roast peanuts until it starts to change colour, now add sesame seeds and roast for few min until sesame seeds turn colour. Transfer to a grinder and grind to a fine powder. Keep aside.
Heat a pan and add 1 tbsp of gingelly oil. Squeeze brinjal and fry on high flame. Reserve the liquid in the bowl. After frying for 5 to 8 min, take it out and keep aside.
Add 1 tbsp oil (if needed) to the same pan. Splutter mustard seeds and curry leaves. Add chopped onions. Saute until light brown. Add ginger garlic paste. Saute for 2 min. Now add tomatoes and saute for 2 min. Now add tomatoes and saute until mushy. Add chilli powder, cumin powder, green chilli, pepper and saute for 2 min more. Mix the spice mix with vinegar and add to the masala. Saute for 2 min.
Mash the soaked tamarind with fingers. Pour mashed mixture through a strainer and add it to the masala.
Add brinjal to the gravy. And cook on medium flame for 5 min. Cook until oil leaves the sides of the pan.
Add 1/2 cup of water and simmer for few minutes. Add the ground powder to the gravy. Simmer for few min. Add more water if needed.
Adjust salt. Curry should be sour and spicy.
Ginger garlic paste - Grind equal quantities of Indian ginger and garlic in a grinder (without water) to a fine paste. This can be stored in a clean, dry jaw in the fridge for upto 2 weeks.
Peanuts - Roasted salted peanuts can be used in this recipe to save time. Roast the sesame seeds and grind it along with roasted peanuts.