Place the 4 cups water in a large saucepan and add peppercorns, carrot, onion and bay leaf. Simmer 10 minutes. Add the chicken breasts and simmer 12 minutes. Let the chicken cool in the poaching liquid then shred.
Halve the rockmelon and papaya and discard seeds. Scoop out the flesh with a melon baller into a salad bowl. Halve the mango, remove the seed and cut the flesh into cubes. Add the mango and chicken to the bowl.
To make the dressing, combine yoghurt, ground cardamom, ground coriander and lemon juice. Season to taste. Toss with the salad.