Marinate chicken pieces for 20 minutes in marinade ingredients: soy sauce, Shaoxing wine, sesame oil and cornstarch. In a separate small bowl mix sauce ingredients: 3 tablespoons light soy sauce, Pixian doubanjiang, dark soy sauce and Shaoxing wine.
Heat wok over medium flame and add 3 tablespoons oil. Add garlic, ginger, scallion whites, dried chilies, Sichuan peppercorns, cumin, star anise and cassia and stir around until mixture becomes fragrant, for about 2 minutes, making sure that it doesn’t burn.
Turn heat up to high and add marinated chicken. Stir-fry until chicken is partially cooked and starting to take on some color, making sure not to burn the spices.
Make a well in the center of the wok, add the sauce mixture and cook briefly. Add 2 cups water, mix well and bring to a boil. Reduce heat to medium-low, cover wok and simmer for 10 minutes for bone-in chicken (5 minutes if using boneless). [Recipe updated Feb 2022, reducing water from 3 cups to 2 cups, which will make plenty of soupy broth for noodles; add more if needed.]
Add potatoes to the wok and return to a boil. Lower heat, cover wok and simmer 5 minutes. Taste, and add salt if needed. Add bell peppers, cover wok and simmer an additional 5 minutes.
Meanwhile, bring a large pot of water to boil and cook noodles according to package directions, aiming to have them done just as the stew is done.
If you would like a thicker consistency to the stew, mash a few of the potatoes with a fork. Just make sure to retain enough sauce for the noodles!
Transfer hot noodles to a large wide plate or bowl and cover with the chicken stew. Garnish with scallion greens and serve immediately.