1. In a large pot, add butter or olive oil, leek, garlic and ginger. Cook gently until leek is fragrant and softened.
2. Add liquid and bring to a simmer over medium heat.
3. Add corn and chicken and bring back to a simmer. Cook for 5 minutes, stirring frequently.
4. Slowly pour in eggs, if using, and stir quite vigorously to form thin strands in the soup.
5. Season to taste and serve, garnished with spring onions.