Combine the stock, tomatoes, soy sauce and sugar in a large saucepan. Bring to the boil reduce the heat slightly and simmer for 2 minutes. Season with a little white pepper and the sesame oil

Add the eggs in a thin stream, while stirring the soup in a clockwise direction, to form thin stream of egg. Let stand for 1 minute, then serve in deep bowls, topped with onions and coriander