1 - 2 chayotes or 2 - 3 courgettes
2 fresh red chillies, seeded
1 onion, quartered
5 mm (1/4 in) fresh lengkuas, peeled
1 lemon grass stem, lower 5 cm (2 in) sliced, top bruised
2.5 cm (1 in) fresh turmeric, peeled
200 ml (7 fl oz) scant 1 cup water
lemon juice
400 ml (14 fl oz) can coconut milk
450 g (1 lb) cooked, peeled prawns
salt
red chilli shreds, to garnish (optional)
boiled rice, to serve