Char the onion and ginger directly over a gas flame or under a broiler until blackened in spots, about 5 minutes. This step adds significant depth to the broth, so don't skip it. Rinse off any loose char.
Toast the star anise, cloves, cinnamon stick, and coriander seeds in a dry pot over medium heat for 1-2 minutes until fragrant.
Add the chicken, charred onion and ginger, and water to the pot. Bring to a boil, then skim off any foam that rises to the surface.
Reduce heat to a gentle simmer and cook, partially covered, for 45-60 minutes, until the chicken is fully cooked and tender.
Remove the chicken, let it cool slightly, then shred or slice the meat, discarding skin and bones, or reserving bones to simmer longer for extra flavor.
Strain the broth to remove the spices and onion and ginger. Return the strained broth to the pot, season with fish sauce, sugar, and salt to taste, and keep warm.
Cook the rice noodles according to package directions, then divide among bowls. Top with shredded chicken and ladle the hot broth over top.
Serve with bean sprouts, basil, cilantro, green onion, lime wedges, and jalapeno and hoisin or sriracha on the side for guests to customize.