Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
     1/2  teaspoon      cumin seeds
     7/8  ounce         fresh ginger -- finely grated
   2      cloves        garlic -- finely
                        chopped
   6                    curry leaves
   3 1/2  ounces        tomatoes -- peeled and chopped
   2      teaspoons     chilli powder
     1/2  teaspoon      turmeric
   1      pound         shelled prawns
   3      tablespoons   white vinegar
                        salt to taste
     1/2  teaspoon      sugar
   1      teaspoon      cornflour

Preparation:

Crush cumin seeds with ginger, garlic and mustard seeds. Heat oil in a pan, add onion and curry leaves and fry until onion is golden. Add tomato, chilli powder, turmeric and 1-2 tablespoons water and cook, mashing tomato under back of a wooden spoon to make thick paste. Add crushed spices and continue to fry for 5 minutes, then add prawns and 4 tablespoons water and simmer for 10 minutes. Pour on vinegar. The sauce may be thickened, if necessary, by adding the cornflour mixed with 1 tablespoon water. Add salt and sugar to taste.