Bring enough water to the point of boiling in a pan and then add the legs of the duck and cook for two minutes. Take the duck out and dispose of the liquid.
In a pot that is clean, put in 6 cups of water ginger slices, garlic cloves whites, scallion whites, salt. As soon as the water is beginning to boil, add duck legs. Allow the water to simmer for another minute and then add all the rice.
Bring the mixture to a boil, and then lower the heat to a moderate simmer. Clean foam off, then cover the pot by putting the lid snipped. Cook for 30 to 35 minutes.
Make sure to check the congee every 10 to 15 minutes or so, and give it a stir, or scrape off foam if required. After 30 to 35 minutes, remove the legs of the duck from the pot. Separate the bones from the meat. Shred the meat , then put bones back in the pot. Let them simmer for another 30 minutes.
In the next 30 minutes take any bones that remain in the congee after 30 minutes. Taste and adjust the seasoning using additional salt, or even fish sauce. Also , check the consistency and adjust it according to your preference by adding a little fluid to even it out , or simmer it for a while to increase the thickness.
Add the shredded duck to the congee, and stir until it is evenly distributed throughout the congee. Transfer the congee to serving bowls and decorate with thinly cut scallions, the herb cilantro Vietnamese coriander and julienned ginger , and black pepper.