Bring vegetable broth to a boil in a saucepan.
Mix cornstarch with cold water, stir into broth, and cook for 2 minutes until slightly thickened.
Season broth with soy sauce, salt, and black pepper; turn heat to low.
Whisk eggs in a small bowl, then slowly drizzle into simmering soup while stirring gently in one direction.
Garnish with chopped spring onions and serve immediately.