Make a pouch out of foil big enough to hold the piece of fish you have picked.
Add the barramundi, wine, sweet chili sauce, and butter to the foil pouch. Seal the pouch, removing as much air as possible.
Cook in/on your fire source of choice at a temperature of about 175 degrees C (350 degrees F) oven for 10 minutes. the foil will puff up from the steam towards the end of cooking. Serve in the foil or tip the fish and juices onto a plate to serve.