In a large pot, combine chicken broth, sugar, fish sauce, soy sauce, sliced ginger, onion, and star anise. Bring to a boil, then simmer for 30-40 minutes.
In the last 10 minutes of simmering, add shredded rotisserie chicken to the broth and let it heat through.
Cook the rice noodles according to package instructions (6-8 minutes). Drain and rinse under cold water.
Place cooked rice noodles in each serving bowl, then pour hot broth and chicken over the noodles.
Garnish with fresh herbs, bean sprouts, jalapeños, and lime wedges.
Notes
Adjust sugar and fish sauce to taste for a balanced flavor; use fresh herbs right before serving for optimal freshness.