Difficulty:[usr 1 ]
Cook the rice in boiling salted water for 20 minutes. Drain it, rinse it under cold water and drain it very carefully.
Peel the prawns and, if they are too large, cut them in half.
Peel the onions and cut them into thin slices. Peel the avocados and cut them into small dice.
Prepare the sauce in a salad bowl, whisking together all the ingredients except the fine herbs. Add all the elements of the salad, mix and keep cool until mealtime. Just before serving, sprinkle with chopped herbs.