Rinse the rice in a sieve under cold running water until the water runs clear, drain well. Bring the water, salt and lemongrass to the boil. Add the rice, boil until almost soft. Add the chilli pepper, cook for a further 1 min. Drain the rice, rinse with cold water.
Combine the lime zest and juice with the oil in a bowl. Add the mango, coriander and rice, mix, season with salt.
Heat the oil in a non-stick frying pan, sauté the prawns for approx. 3 mins., season, serve with the rice salad. Scatter over the peanuts.