Arrange the fish in a serving dish, season and sprinkle with Cayenne pepper. Peel and slice the onion and garlic thinly. Chop parsley and add to sole. Pour lime juice and coconut milk over dish and cover. Leave to chill for 15 minutes. Meanwhile, wash the courgettes, top and tail and slice into 24 sticks, lengthways. Steam for five minutes, or boil for three, then run under cold water and dry. Keep the marinade to one side, strain fish, put a courgette stick in the middle of each fillet and roll up. Skewer four fish rolls on each kebab stick and barbecue for three minutes, turning frequently and drizzling with marinade.