Boil rice noodles per package instructions. Drain and set aside.
Heat oil in a pot. Add star anise and cinnamon; toast until fragrant.
Add ginger and garlic, cook until lightly browned.
Pour in chicken broth, fish sauce, soy sauce, lemongrass, half the jalapeño, and shrimp shells. Simmer 15 minutes.
Remove spices and shells using a fine sieve.
Add shrimp and bok choy. Cook 2 minutes until shrimp turn pink.
Stir in lime juice and cilantro.
Divide noodles among bowls, ladle broth, and garnish with jalapeño and cilantro.
