Simmer Chicken: Place whole chicken, charred onion, and ginger in a pot. Cover with water and simmer for 45-60 minutes until the chicken is cooked.
Char Aromatics: Char onion and ginger over an open flame or under a broiler until blackened, then peel.
Shred MeatRemove chicken, let it cool, and shred or slice the meat. Return bones to the pot to continue simmering for another 1-2 hours for a deeper flavor.
Toast SpicesToast star anise, cinnamon, and coriander seeds until fragrant, then add to the broth for the final 30 minutes.
Assemble: Combine noodles, chicken, and hot broth. Garnish with lime, cilantro, and sliced scallions