Soak onion slices in cold water for about 2 hours, if you like a milder onion flavour. Drain and set aside.
Bring a large pan of salted water (at least 3lt) to the boil. Stir in the rice bring back to a medium boil and cook for 10 minutes. Drain, rinse in hot water then drain again for 5 minutes. Transfer rice to a bowl, season well and mix in the dressing. Leave to cool.
Stack cucumber slices, six or so at a time and cut into shreds. When rice is cold mix in onion, cucumber, parsley and olives. Adjust seasoning, cover and chill.
Mix the turkey and prawns together. Season and mix in the lime juice.
Stir mayonnaise, yogurt, milk and chutney to a smooth sauce. Stir into the turkey and prawns along with the almonds and herbs. Adjust seasoning.
To serve, spoon the rice around the edge of a large oval platter and then tip turkey mixture in the centre. Garnish with herbs and serve lightly chilled but not too cold.