Slit open the chillies from top to tail, taking care to leave the stalks intact. Scrape out the seeds. Divide the shredded basil and chopped ginger between the chillies and generously season the chiilies inside.
Shell the prawns, leaving the tail section intact. Place a whole prawn inside each chilli, leaving the tail poking out of the pointed end. Smear a little butter on top of each prawn, then squeeze the chillies together to enclose the prawns.
Thread 3 chillies, alternating colours, onto 2 short, parallel bamboo skewers so that the chillies look like the rungs of a ladder - you will need to soak the skewers for 20 minutes before using them. Repeat to make 8 ladders.
Cook the chillies over fairly hot coals for about 5 minutes, turning frequently until they are softened and a little charred, and the prawns are cooked through. Serve with wedges of lemon. Delicious.