Preheat your grill to 200c and season the chicken breasts with a good pinch of salt and pepper. Put the chicken under the grill and cook for 9-12 minutes, turning it halfway.
It's difficult to be completely specific about timings when grilling chicken as the breasts may vary in size and grills are not all the same. The important thing is to check that it's cooked through - check both breasts after 9 minutes by making a small incision into the chicken and if it's still pink, cook for another 2 minutes then try again.
Once you've put the chicken under the grill to get started, you'll have plenty of time to make the salsa. Get straight on and peel then finely chop half a small red onion. Put it in a mixing bowl and add half a chilli, deseeded and finely sliced. Roughly chop the coriander and add that to the bowl. Check the chicken now and it should be ready to turn over.
Place the mango on the chopping board flatter side down (the mango will come to rest on it's flatter side). Cut straight down either side of the core. Turn the mango so that a cut side is flat on the surface and do the same again - cut down the other two sides of the core. You should be left with a rough rectangle with the core in the middle.
Take one of the pieces you've cut off and slice lines about a centimetre apart vertically and then horizontally all the way to (but not through) the skin. The result should be lots of little cubes of mango still attached to the skin.
Press the outside of the skin to push all the cubes out a bit - this should make it easy to simply cut away the cubes of mango clean from the skin.
Do this with all four pieces of the fruit and then cut what you can away from the remaining core. Add the mango chunks to the bowl and then mix everything together.
Add a small pinch of salt and pepper and a teaspoon of balsamic vinegar. Mix again and it should be about time to remove the chicken from the grill. Place the chicken on a board and slice through it at an angle.
To serve place the chicken on one side of the plate and spoon over some of the salsa. Take a small handful of salad leaves and carefully place them to the side and you're done!
I hope that you enjoy it!