Preheat your oven to 350°F. Roasting the aromatics is the first step to building a great flavor base. Place the onion, ginger, and chicken bones in a roasting pan. Roast them for one hour, stirring them halfway through. This enhances the flavors significantly. Once roasted, remove them from the oven and let the onion and ginger cool.
After cooling, peel the onion and cut it in half. Slice the unpeeled ginger into thin pieces; there's no need to peel it. Now, combine the onion, ginger, chicken bones, water, salt, and brown sugar in a large stock pot.
Bring the mixture to a boil over high heat. Once boiling, reduce the heat and let it simmer for three hours. During this time, ensure the water level stays about one inch above the bones. You can add more water if needed.
Once the stock is ready, use a large slotted spoon to remove most of the bones and onion chunks from the pot. Strain the stock through a fine-mesh sieve into another heatproof bowl or pot. Let it chill for at least one hour or, if possible, overnight. This allows the flavors to deepen and the fat to congeal on top.
To prepare the fried shallots, heat enough vegetable oil in a medium saucepan until it reaches 340°F. Carefully add the shallots and fry them, stirring constantly until they turn light golden brown, which should take about 4 to 6 minutes. Watch closely to prevent burning. Once golden, transfer them to a paper towel-lined plate to drain and set aside.
In a large pot, bring water to a boil again. Once boiling, add the chicken, scallions, ginger, and salt. Cook for 15 minutes, then turn off the heat, cover the pot, and let it sit for 25 minutes. This method helps keep the chicken juicy.
While the chicken is resting, prepare an ice-water bath in a large bowl. Once the chicken is done cooking, carefully remove it from the pot using tongs and submerge it in the ice-water bath. This stops the cooking process and firms up the meat. Discard the cooking liquid or store it for another use.
Let the chicken cool for about 20 minutes, or until it’s cool enough to handle. Remove it from the water, pat it dry, and shred the meat from the bones. You should end up with about four cups of shredded chicken.
Bring the strained stock back to a simmer over medium-high heat. Taste and adjust the seasoning with more salt or even a splash of fish sauce if desired.
Prepare the rice noodles according to the package directions. Distribute the cooked noodles evenly among serving bowls.
Finally, prepare an assortment of garnishes. On a large platter, arrange the basil, bean sprouts, lime wedges, jalapeños, and fried shallots. Place this platter on the table so everyone can customize their bowls.
Top each bowl with about three-quarters of a cup of the shredded chicken, then sprinkle with the sliced scallions and cilantro. Ladle the hot stock over the noodles and chicken, finishing with a sprinkle of fried shallots. Serve immediately, allowing everyone to add their favorite garnishes.
