850 ml (1 1/2 pints) fish stock
2 tablespoons soy sauce
2 fresh red chillies, de-seeded and chopped finely
1 garlic clove, chopped
1 teaspoon caster sugar
175 g (6 oz) carrots, sliced into matchsticks
1 red pepper, de-seeded and sliced thinly
175 g (6 oz) tiger prawns, peeled
100 g (3 1/2 oz) thin egg noodles
100 g (3 1/2 oz) water chestnuts, sliced
6 spring onions, sliced
2 tablespoons chopped fresh coriander, to garnish