Pour the water into a large saucepan. Add the stock cubes and whisk over a high heat until the stock boils. Add the red capsicum strips and corn. Bring back to the boil, then add the chicken strips and immediately reduce the heat to low. Cover and simmer gently for 5 minutes.
Uncover the pan and bring the soup back to the boil. Sprinkle the broccoli into the soup, but do not stir the pieces in. Leave the broccoli to cook on the surface of the soup, uncovered, for 3–4 minutes until just tender.
Take the pan off the heat. Stir in the sherry, chives, tarragon and salt and pepper to taste. Serve at once.