1. Heat oil in a medium pot. Add tomatoes and saute for 2 minutes.
2. Add in 2/3 of the spring onions and saute to release aroma, about 1 minute.
3. Add stock and bring to the boil. Reduce heat and allow to simmer for 2 minutes.
4. Meanwhile, whisk eggs in a bowl and set aside.
5. Make cornflour slurry by adding cornflour and water in a small bowl and mixing. Pour slurry into the soup and stir to thicken. If you like your soup thicker, you can add in more cornflour slurry to adjust to your liking.
6. Remove pot from the heat. Pour whisked eggs into the soup at a height, gently stirring the soup to create egg ribbons in the soup. This will only take a few seconds.
7. Taste and season with salt and pepper.
8. Garnish with remaining spring onion and serve hot.