Heat the broth and soy sauce in a medium pot over medium-high heat.
While the broth is heating, whisk the eggs with the salt and garlic powder in a spouted measuring cup.
When the broth starts to boil, use a non-slotted spoon (such as a wooden spoon) to stir the soup. Slowly drip the egg into the broth, continually stirring as you pour the eggs. Make sure to stir in the same direction.
As soon as you're done pouring the eggs in, remove the soup from the heat and pour it into soup bowls. Garnish with chopped green onions and serve.
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Notes
If you don't have homemade chicken broth on hand, it's fine to use a store-bought one. It's best NOT to use a low-sodium one in this recipe. While great as a base in many other recipes, it lacks flavor, and in this recipe, it's going to be noticeable.
In traditional recipes, cornstarch is usually added to the broth to thicken it. In my version, I skip the cornstarch. While the soup is not as thick as the ones you'd get at a restaurant, I find that the egg ribbons provide plenty of thickening, and the soup is wonderfully thick and creamy.
While this soup works well as a first course, you can also serve a bowl as a light lunch, especially if you add tofu cubes to the soup after you've stirred the eggs into it. Another way to make it into a complete meal is to add cooked chicken cubes or tiny cooked meatballs.
You can keep this soup in an airtight container in the fridge for 3-4 days and reheat it, covered, in the microwave. The leftovers should be thoroughly reheated to 165° F before serving, and the eggs might become rubbery after reheating. So, while keeping the leftovers is possible, it's best to only make as much as you can finish right away.