
Heat the oil in a large 6-quart pot over high heat. Place the onion halves and ginger cut-side down and char for about 2 minutes, then turn and char the other side for 2 minutes more.
Add the water, chicken thighs, cilantro, star anise, cinnamon stick, fennel seeds, coriander seeds, fish sauce, and sugar. Do not add the salt yet.
Bring the pot to a gentle simmer, then reduce the heat to low. Cover with the lid slightly ajar and simmer very gently for 1 1/2 hours, skimming off any foam from the surface once or twice.
Remove the chicken and transfer it to a plate to cool slightly. Strain the broth into a clean pot, discarding the solids.
Measure the strained broth. You should have about 1.5 liters; if you have more, simmer it uncovered to reduce, and if you have less, add a little water.
Stir the salt into the broth and bring it back to a gentle simmer. Taste and adjust if needed; the broth should taste slightly salty on its own because the noodles will mellow the flavor.
Remove the skin and bones from the chicken, then shred the meat into bite-size pieces. Keep the broth warm while you prepare the bowls.
Arrange the bean sprouts, Thai basil, mint, cilantro, lime wedges, hoisin sauce, sriracha, and sliced red chilies on the table or a serving platter.
Cook the rice noodles according to the package directions just before serving. Drain them very well so they do not water down the broth.
If needed, briefly warm the shredded chicken by dipping it into the hot broth. Divide the noodles among serving bowls and top with the chicken.
Ladle about 1 1/2 cups of hot broth into each bowl. Finish with sliced green onions and any toppings you like.
Serve immediately with a squeeze of lime and extra hoisin or sriracha on the side.




