Peel the prawns and devein them, then rinse in cold water. Peel the shallots and cut into small dice. Shell and finely chop the pistachios. Destalk the coriander leaves.
Toast the cumin, coriander seeds and peppercorns in a dry heavy pan over a low heat for 2-3 minutes, stirring. Remove from the heat, cool and grind to a powder.
To make the stuffing: chop the whiting into pieces and put in the food processor. Chop the prawns and put half of them in with the whiting. Add the crab meat, shallots, spices, egg whites, coriander, oregano leaves if using, and salt. Process to a smooth paste.
With the machine working at full speed, pour the cream in through the feeder tube in a thin stream until incorporated. Scrape out into a glass bowl and stir in the remaining pieces of prawn and the chopped pistachios. Pack down, cover with film and chill for up to 4 hours, or until you are ready to make the börek.
To make the börek: remove the filo from its box and cover with a slightly damp cloth. Taking one sheet at a time, cut it across in half and put a dessertspoon of mousseline on each half and fold and wrap as described. Do not overfill or the package may leak.
Melt the butter and brush the böreks with it. Place them on a baking sheet, not touching each other.
Serve hot with wedges of lemon. They are also nice warm or at room temperature.
This is rather a grand and expensive mixture, but you can dispense with either the crab meat or the prawns, increasing the percentage of white fish, and still end up with a very good result. Alternatively, you could move the dish even further up market by incorporating lobster meat into the mix.
© 1995 Alastair Little. All rights reserved.