1. Cut a criss-cross pattern about ½cm deep across the top of each chicken breast and place in a shallow dish.
2. Using a zester, remove the zest of 1 lime and squeeze the juice. Pour the juice over the chicken, then scatter over the zest. Mix the sunflower oil, ½ tsp cumin and one of the chillies, coarsely chopped, then pour this mixture over the chicken. Cover and leave to marinate in the fridge for 3-6 hours.
3. To make the salsa, peel the mango and cut away the flesh. Cut into 1cm dice and place in a bowl. Add the grated zest and juice of the remaining lime, the olive oil, red onions, the remaining red chilli, deseeded and finely diced, the remaining cumin and the fresh herbs. Mix well, season and cover. (The salsa can be prepared up to 24 hours in advance.)
4. Preheat the grill and cook the chicken under a medium heat for 20-25 minutes, until thoroughly cooked through.
5. To serve, place the cooked chicken on a bed of mango salsa and garnish with fresh coriander.