Mix all marinade ingredients together and combine with prawns. Leave to marinate for at least 30 minutes, or overnight if you have the time.
When ready to cook, Preheat BBQ to medium high heat. Lift prawns out of marinade (reserving any leftover marinade) and thread 3 prawns (or 6 smaller prawns) on to each bamboo skewer.
Season prawns with salt and cook on BBQ until just cooked through, about 2-3 minutes, turning once.
Heat remaining marinade in a small pot on the stove top, or in the microwave. Then mix with yoghurt and coriander.
Serve prawn skewers with yoghurt sauce to dip. Alternatively remove prawns from skewers and toss with mango, avocado, cherry tomatoes and the yoghurt sauce.