Combine broth, brown sugar, fish sauce, star anise, cloves, ginger and cinnamon stick in a 5- to 6-quart slow cooker. Add chicken breasts, meat-side down. Cover and cook on High for 4 hours (or on Low for 8 hours).
Transfer the chicken to a cutting board. Remove spices and discard. Add noodles and bok choy to the slow cooker. Cover and cook on High for 30 minutes.
Remove the chicken from the bone and shred with two forks. When the noodles are tender, stir in the shredded chicken. Serve bowls of soup with bean sprouts, basil, mint, cilantro, sliced chile and lime wedges on the side so everyone can add their own toppings.
TIPS & NOTES.
To prep ahead: Combine seasonings with broth; prep chicken; cover and refrigerate separately for up to 1 day. | Equipment: 5- to 6-quart slow cooker.
Tip: Add star anise, named for its star-shaped pods, to Asian-inspired dishes to lend distinctive licorice-like flavor. Look for it with other bulk spices in natural-foods stores, in Asian markets or online at penzeys.com.
For easy cleanup, try a slow-cooker liner. These heat-resistant, disposable liners fit neatly inside the insert and help prevent food from sticking to the bottom and sides of your slow cooker.