1/2 teaspoon cumin
1 teaspoon mustard seed
1/2 inch ginger
1/4 teaspoon turmeric
2 cloves garlic
1/2 teaspoon cayenne, or to taste
2 medium onions
1/4 cup white vinegar
2 lbs raw shrimp, peeled and deveined
1 tablespoon oil
salt to taste
2 large tomatoes, chopped
2 medium potatoes, cooked and quartered
Grind together the cumin, mustard seed, ginger, turmeric. garlic, cayenne, one of the onions and the vinegar in an electric blender. Combine with the shrimp and set aside for 1 hour to marinate.
Heat the oil and brown the remaining onion which has been thinly sliced. Put in shrimp mixture and fry for 2 or 3 minutes. Add salt, water and tomatoes. Simmer 10 minutes. Add potatoes and simmer until heated through.