1. Set aside the spring onions, bean sprouts and corn flour till the end of cooking.
2. Combine all other vegetables, stock, spices, sauces and vinegar in a large pan and cook on low heat.
3. Add chicken pieces when it comes to a boil.
4. Cook five minutes longer, then dissolve corn flour in 1 cup of stock and add to soup.
5. Stir using a wooden spoon till the soup thickens.
6. Add beaten egg and stir.
7. Heat before serving, add sesame seed oil, bean sprouts and spring onion.