Place ginger and onion on a small baking sheet. The top of the onion should be about 4″ from the oven’s heating element. Set to broil on high for 15 minutes. Turn the onion and ginger occasionally, to get an even char. The skin should get dark and the onion/ginger should get soft. After cooling, rub to get the charred skin off the onion and use a butter knife to scrape the skin off the ginger. Slice ginger into thick slices and slice onion into chunks.
In a large stockpot, fill with water and boil. Cut the chicken breast meat off the chicken and reserve. With the rest of chicken whacking hard through the bones to get sections about 3″ big. The more bone that is exposed, the more marrow that gets in the broth making it more flavorful. When the water boils, add chicken sections (not breast) and boil on high for 5 minutes. Foam should rise to the top. Drain and rinse your chicken of the scum and wash your pot thoroughly. Refill with about 4 quarts of clean, cold water.
Add chicken, chicken breast meat, onion, ginger and all of the spices (tied in a cheesecloth or use refillable tea pouches- I also like to roast the spices in a dry pan for a couple minutes to bring out the flavor) in the pot and cover. Turn heat to high – let it come to boil, then immediately turn heat to low. Prop lid up so that steam can escape. After 15 minutes, remove the chicken breasts, shred with your fingers when cooled and set aside (you’ll serve shredded chicken breast with the finished soup). With a large spoon, skim the surface of any impurities in the broth. Skimming every 20 minutes ensures a clear broth. Simmer a total of 1-1/2 hours. Taste and adjust seasoning with more fish sauce or spices.
Strain the broth, discard solids. Prepare noodles as per directions on package. Ladle broth, add shredded chicken breast and soft noodles in each bowl. Have side ingredients set at table for each person to add to their bowl.