If using tiger prawns, shell and devein. Cover with salted water and swirl to clean, then rinse under cold running water and drain well. Cook in a preheated heavy frying pan for 1½-2 minutes over a medium heat, tossing until opaque. Remove from the pan and leave to cool. If using pre-cooked Atlantic prawns, shell and reserve.
Toast the cumin seeds in a dry heavy pan over a low heat for 2—3 minutes, stirring, and reserve.
Dice the cucumber small and put into a large bowl. Peel, smash and finely chop the garlic. Add to the cucumber, then pour over the yogurt and season with 1 teaspoon each of salt and black pepper.
Thin the soup with iced water until you have a pourable consistency. Taste and adjust the seasoning and chill for 1 hour.
Ladle the soup into individual bowls. Arrange 5 tiger prawns on each or, if using the smaller prawns, divide them equally. Scatter mint leaves on top and strew over a few cumin seeds.
© 1995 Alastair Little. All rights reserved.