In a food processor combine all marinade ingredients and blend to a thin paste.
Pour over the prawns to marinate in refrigerator for at least 2 hours or overnight.
Tiki Mango Salsa:
Remove the 2 flatter sides of the peeled mangoes (the cheeks) as close to the stone as possible, then scrape off the remaining flesh and dice into small squares.
Bind the diced salsa ingredients with the mango and refrigerate until required.
To prepare lemongrass skewers:
Soak the lemongrass stalks for the skewers in warm water for 20 minutes to soften.
Make an incision with a small, sharp knife in the top and bottom of each prawn.
Cut away the thin end of the lemongrass and split the lemon grass stalk down the middle into halves.
Make an incision in the centre of each lime leaf.
Thread a prawn through the lemongrass followed by a lime leaf then a prawn, then a leaf.
Continue this process with 3 prawns per skewer.
Lay skewers onto a tray and brush with peanut oil just before cooking.
Preheat the barbecue in preparation to cook prawns.
Place the skewers on the barbecue just to seal and char the meat, then transfer to a cooler part of the grill to cook gently for 2-3 minutes per side.
Place 2 skewers and 3-4 tbsp of salsa on each plate.