Preheat the barbecue. Mix the mango with the chopped mint, chilli and lime juice and zest. Set aside.
Put the egg in a small bowl and put the coconut and black pepper on a plate. Dip the prawns into the egg, then roll in the coconut and black pepper mixture to coat. Thread 2-3 prawns on to each skewer.
Wrap foil around pairs of bamboo skewers and barbecue for 2-3 minutes on each side. Remove the foil and barbecue for a further 30 seconds. Garnish the mango salsa with the mint leaves and serve with the prawns.