Clean the prawns, devein, wash & chop into small pieces. Marinate in the salt and turmeric powder for 15 - 30 minutes.
Dry roast the spices given in the balchao masala from pepper to cloves and grind with the chillies, ginger, garlic, tamarind and ACV.
Thinly slice the onions, ginger and garlic. In a wide mouthed pan dry fry the onions for a minute or two. Then add 2 tbsp of oil, the ginger garlic and curry leaves. Fry well and keep aside.
In the same pan add another 2 tbsp of oil and shallow fry the prawns, till the prawns slightly brown and all the water evaporates. Transfer to a plate.
Now add back the fried onion mixture to the pan, and fry for a few more minutes. Add the ground balchao masala and saute well.
Add 2 more tbsp of ACV to thin out the gravy, salt as needed, jaggery, turmeric powder and asafoetida.
Mix well and add the fried prawns. As the water dries out add two more tbsp of oil. Cook till it oozes out oil.
Cool down completely, before transferring to an airtight container, preferably glass.