Place the water in large saucepan with bones, brown onion, carrot, three-quarters of the ginger and 2 chilli halves; bring to a boil. Reduce heat; simmer, covered, 2 hours.

Strain broth through muslin-lined sieve or colander into large heatproof bowl; discard solids. Allow broth to cool; cover, refrigerate.

Meanwhile, chop remaining chilli finely; combine in bowl with remaining ginger, pork, garlic, green onion, water chestnut, coriander, oil, 2 teaspoons of the wine and 1 teaspoon each of the sauce and the sugar.

Place 1 level tablespoon of filling in centre of each wonton wrapper; brush edges with a little water. Gather edges around filling; pinch together.

Skim and discard fat from surface of broth. Return broth to large saucepan with remaining wine, sauce and sugar; bring to a boil. Add wontons, reduce heat; cook, uncovered, about 5 minutes or until wontons are cooked.

Divide watercress, mushrooms and wontons among bowls; ladle broth into bowls.