Add the green onions to the chicken broth in a 6-cup (1.5 L) microwave-safe bowl.
Cover and microwave at HIGH 10 minutes.
Beat the eggs with the soy sauce.
Slowly pour this mixture into the hot broth, stirring constantly.
The eggs will form long filaments and will cook very quickly, simply from the heat of the broth.
Add the watercress leaves.
The soup will resemble scrambled eggs.