Grind the garlic, chili, cumin seed, mustard seeds, peppercorns & tumeric together in a processor with 2 Tablespoon of vinegar to act as a lubricant. Heat the oil in a pan and fry the onion paste over moderately low heat until light brown. Add the ground spices and continue to fry the mixture until it turns reddish, with a 'crumbled' look. Add the prawns & cook, stirring frequently for 10 minutes. Add the balance of the vinegar, the water and salt and continue to simmer, uncovered, for 5 minutes more. There will be very little sauce. Serve warm VARIATION: The prawn vindaloo can be prepared as a proper pickle, which means that it is a bottled (or refrigerated condiment) used now and then with other foods as an adjunct to the meat or fish dishes being served. Should you wish to prepare this as a pickle, follow the instructions, but omit the onions & and the water & cook the prawns separately in 2 Tablespoon of oil before adding them to the mixture. SERVES: 6 SOURCE: _The Varied Kitchens of India_, the Parsi Kitchen chapter posted by Anne MacLellan