Whisk 1/2 cup of chicken broth with the cornstarch in a small bowl until smooth to create a slurry. Set aside.

In a medium pot, combine the remaining 5 1/2 cups of broth, garlic, ginger, and white parts of the green onions. Bring to a boil over medium-high heat, then lower the heat and simmer for 5 to 8 minutes.

Stir the slurry into the simmering broth and cook for 1 to 2 minutes until the soup thickens.

Reduce heat to low, and while stirring in slow circles, pour in the beaten eggs in a thin stream, allowing them to cook into soft ribbons.

Once the soup reaches a boil, remove it from the heat immediately. Discard the garlic and ginger pieces.

If desired, stir in toasted sesame oil for added flavor.

Ladle the soup into bowls and garnish with green onion greens. Add red pepper flakes or sesame oil if desired, and serve hot.