1 kg peeled prawns
30 ml coriander seed
15 ml cumin seed
1 kg crushed tomatoes
14 crushed garlic cloves
6 bay leaves
5 cm finely chopped fresh ginger
2 1/2 ml ground black pepper
2 1/2 ml cardamon seed
2 1/2 ml cinnamon
2 1/2 ml cloves
2 1/2 ml cayenne
10 ml ground mustard seed
15 ml turmeric
250 ml wine vinegar
2 medium onions
2 medium potatoes
15 ml butter

Lightly roast the cumin seed and coriander seed by frying with no oil for a minute or so, stirring constantly.
Grind these and combine them into a paste with the other spices, the garlic, ginger, and the vinegar.
Add the prawns to the marinade and mix well. Refrigerate for 3-24 hours while mixing every few hours as convenient.
Finely chop the onions and potatoes and saute them for 5 minutes in the butter.
Add prawns and spice paste and simmer over low heat for half an hour.