Steam corn until tender. Cool and then cut corn kernels from cobs. Heat the stock in a medium pan and add the corn, chicken and ginger. Simmer mixture, uncovered, for 5 minutes.
Combine cornflower and water in a small bowl and mix to a smooth paste. Add to the pan, stirring until soup mixture thickens.
Add spring onion and sesame oil and stir to combine. Add salt and pepper to taste. Serve immediately.