This soup can be made easily in the workplace. Pack the bouillon cube, scallions, and watercress in an airtight container; stir in hot water when ready to serve. The croutons can be made ahead and packed separately.
This is a great soup! It is so easy and nutritious. I have made this soup for multiple small cooking demonstrations at nursing home and all the staff and patients absolutely love this soup. Many people have never tried watercress before and have no idea about it's nutrition or intersting history. I highly recommend this soup! It is also is easy to change-up or make more hearty, it tastes great with diced potatoes, snow peas, or any other veggie you want to throw in when making at home.