In large pot, add 6 cups water, sliced ginger, 1 quartered onion and 1 stalk of scallion (tied in a knot), the turmeric, a pinch of salt. Bring to boil over high heat. Lower the chicken into the pot and bring to boil again. Skim any impurities. As soon as the water boils, reduce the heat to low, cover the pot and simmer for 10 minutes (make sure the water is not boiling, just simmering). After 10 minutes, turn off the heat and let the chicken continue to cook in the warm pot for 15 minutes. Test that the chicken is well cooked by piercing the thick part of the thigh and if juice runs clear, it's cooked.
Remove the chicken from the pot and add it to a bowl of iced water for 5 minutes to firm up the meat and halt the cooking. Put the chicken on a chopping board. When cool enough to handle, remove the bones. Add the bones back to the pot and cook for another 30 minutes, to make the broth. Use part of the broth to cook the rice, and the remainder as a broth served on the side.
Shred the chicken meat. Set aside to cool (or cover and refrigerate).
While the chicken is cooking, wash and dry the Rau Ram, slice finely. Set aside
Slice the remaining onion very thinly. Soak the sliced onion in the vinegar mixed with sugar and nuoc mam.
To cook the rice - Rinse the rice until water is clear. Add the rice to rice cooker and the chicken broth quantity as per your rice cooker instructions. For my rice cooker, I add 2 and 1/4 cup of broth. Cook as per the rice cooker instructions.
To assemble: Mix the shredded chicken with the drain sliced onions, add salt & pepper to taste. Just before serving, add the Rau Ram (Vietnamese coriander) and mix. Serve with the cooked chicken rice. Scoop the remaining broth into small bowls, sprinkle chopped scallions, to serve on the side.