Serves2 (light main course) or 4 (first course) 
                    
                
                
                    
                        
                            - Active time:15 min
 
                        
                            - Start to finish:45 min
 
                        
                    
                
             
            
            
                
                
                
    
      
          
          
          
              
              
              
          
          
          
          
          
              
              
              December 2008
            
          
          
      
  
                
                
            
            
            
                It’s only natural to use leftover chicken broth (from Blade Steaks with Rosemary White-Bean Purée) to make chicken soup. But what a soup! Steeping ginger and scallion greens in the stock and then poaching the chicken in it is a quick way to achieve a depth of flavor. The final soup is enriched with silky ribbons of just-cooked eggs, shreds of tender chicken, and fresh rings of scallion. Best of all, this satisfying soup is easy enough to pull together after work. 
            
            
            
            
            
                
                    
                    
                    
                        
                            
                            
                            
                                
                                    
                                        - 
                                            6
                                            
                                            scallions, divided
                                            
                                        
 
                                    
                                        - 
                                            2
                                            cups
                                            water
                                            
                                        
 
                                    
                                        - 
                                            1 1/2
                                            cups
                                            reduced-sodium chicken broth
                                            
                                        
 
                                    
                                        - 
                                            1
                                            
                                            (2-inch) piece peeled ginger, sliced
                                            
                                        
 
                                    
                                        - 
                                            1
                                            
                                            skinless boneless chicken breast half (6 to 8 oz)
                                            
                                        
 
                                    
                                        - 
                                            2
                                            
                                            large eggs, lightly beaten
                                            
                                        
 
                                    
                                        - 
                                            1/4
                                            teaspoon
                                            white pepper (optional)
                                            
                                        
 
                                    
                                
                            
                         
                    
                 
            
            
            
            
            
                
                    
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Accompaniment:
                            
                            Asian sesame oil
                         
                    
                
            
            
            
            
                
                    
                    
                    
                        
                            
                                
                                
                                
                                    
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Smash 3 scallions and cut into 2-inch pieces, then put in a 2-qt saucepan with water, broth, ginger, and 3/4 tsp salt. Bring to a simmer, then poach chicken at a bare simmer, uncovered, until just cooked through, 12 to 15 minutes. Transfer chicken to a cutting board and let broth steep, covered, 10 minutes.
                                         
                                    
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Meanwhile, chop remaining 3 scallions and shred chicken.
                                         
                                    
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Discard scallions and ginger from broth and bring to a brisk simmer. Add beaten eggs in a slow stream, stirring constantly. Remove from heat and stir in scallions, chicken, and white pepper (if using). Serve drizzled with sesame oil.