Clean the dried scallops. Add the dried scallops into a bowl of water and let sit for at least 10 minutes. The water will clean out the dried scallops.
Roast the onion and ginger. Preheat the oven to broil. Broil the yellow onion and ginger root for 10-15 minutes until you see charred edges on both.
Make the herb bundle. Toast the coriander seeds and fennel seeds on the stove in a small pan for 1-3 minutes until you smell a toasty aroma. Add to a cheese cloth and tie it tight with some butchers twine.
Par boil the chicken to clean it. Add chicken to a large soup pot and cover with water until it just covers the chicken. Bring to a boil. After it boils, remove the chicken and pour out the water. This allows you to clean the chicken and obtain a clean broth.
Make the broth. Now you are ready to make the broth! Add the chicken back to the soup pot and cover with fresh water until it just covers it. Add in the roasted onion, ginger, dried scallops, daikon, and herb bundle. Bring to a boil and then lower to a simmer. Simmer for 30 minutes.
After it has simmered for 30 minutes, take out the chicken and rest the meat about 10 minutes or until it is cool enough to handle. Continue simmering the broth while you are waiting. Once the chicken is cool enough to handle, shred all the meat. Add the bones back to the soup to cook further. Add the chicken broth and simmer for another 2.5 hours. Taste the broth to make sure it is seasoned to your tastes. If it tastes bland, add more salt.
Once the soup has finished cooking, remove your solids, and strain it through a fine mesh sieve into another soup pot. The purpose of this is to get the cleanest broth possible by removing any small solids in the soup.
Make your green onion and cilantro toppings. While the soup simmers, mince your green onions and cilantro. Set them aside in the fridge while you wait for your soup to finish.
Boil the noodles. When you have about 10 minutes left in simmering time, cook your noodles. If using fresh noodles, cook in boiling water for 2-3 minutes, and if using dried noodles, cook in boiling water for 5-10 minutes.
Putting it all together. Once the soup has finished cooking, add some noodles, shredded chicken, minced green onion, minced cilantro, fried shallots, and a dash of fish sauce (optional) to a bowl. Ladle soup over the top and serve.