Prawn cocktails with coriander lime dressing

Process 1 tbs no-fat Greek-style natural yoghurt, 1 tbs fresh coriander leaves, 1 tsp lime juice and ¼ tsp fish sauce in a food processor until smooth. Season dressing with salt and pepper. Line the sides of a 1 cup (250ml) capacity serving glass with 2 baby cos lettuce leaves. Finely shred another 3 leaves and layer with 5 cooked medium king prawns (peeled, deveined, tails intact) in the glass. Top with dressing and serve.