Bring water to a boil in a stock pot, add the belly pork and chicken carcasses. Boil for 4-5 minutes then remove the belly pork and leave aside to cool. Slice the meat into thin strips. Blanch the prawns in the stock until they change colour. Dish out and slice into halve lengthwise. Continue to simmer the stock for half an hour. Add seasoning to the stock. Thicken the stock with the cornflour mixture. Keep the stock hot over a low heat.