Mix together the tomato
puree, water, ginger, cayenne, lemon juice,
salt, pepper and sugar. Heat the oil and
fry the mustard seeds until they start
crackling.
Add the garlic then the
prawns and stir-fry for 2 minutes. Pour in the
sauce mixture and stir over a low heat until the
sauce starts bubbling. Serve at once with rice
and vegetables.