1: Bring a large saucepan of salted water to the boil over a high heat. Drop in the corn cobs and boil for 5–8 minutes until the kernels are tender. Remove the cobs from the water and set aside to cool. Meanwhile, preheat the oven to 180°C/Gas Mark 4.
2: Cut the corn kernels away from the cobs and set aside. Chop the cobs into small pieces, then put them into a roasting tray and roast for 10–15 minutes until they are toasted and a little singed. Place the maple syrup and the soy sauce in a pan over a high heat and bring to the boil, stirring to dissolve the maple syrup. Continue boiling until the mix begins to caramelise, then pour in the chicken stock and return to the boil. Add the toasted corn cobs, reduce the heat and leave the stock to simmer, uncovered, for 15 minutes.
3: Heat the rapeseed oil in another pan over a low heat. Stir in the ginger and garlic, then add the chicken breast and continue stirring for a further 4–5 minutes until the meat is cooked through and the juices run clear. Strain the infused chicken stock through a fine sieve into the pan and bring to the boil.
4: Stir the water into the cornflour to make a paste, then whisk this into the stock. Return to just below the boil, then reduce the heat and simmer for 2–3 minutes until the soup thickens slightly. Add the sweetcorn kernels and the lime juice and season. Whisk the egg, then pour it into the simmering soup, whisking all the time so they egg cooks into thin strands.
5: Ladle the soup into bowls, sprinkle with spring onions to garnish and serve immediately.