Soak the brain in saltwater for two hours. Clean the brain thoroughly removing all the blood vessels and the thin skin. Drain the water and place the brain in a vessel. Add little salt, turmeric, coriander powder, chilli powder, vinegar and some water to the brain and boil for about ten minutes.
In another pan pour some oil and and saute sliced onions and curry leaves over medium fire. When it changes colour, add green chillies, ginger and garlic paste. Saute till the oil comes out. Add curry leaves, garam masala and pepper powder. Add some water and when it boils, add the cooked brain and the remaining gravy. Sprinkle salt to taste. Saute the brain gently in the gravy.Cook on slow fire until the water dries. Again add fresh curry leaves before turning off the fire.