Follow the steps in order for the best result.
Dice the chicken thighs into small, bite-sized pieces. Thoroughly coat the chicken pieces in cornstarch, ensuring to shake off any excess.
In a wok or deep skillet, heat a generous amount of oil suitable for deep-frying. Fry the cornstarch-coated chicken until fully cooked and golden brown. Once cooked, remove the chicken and drain on a wire rack or paper towels to remove excess oil.
Pour out most of the oil, leaving about 1-2 tablespoons in the wok. Heat the oil over medium-high heat. Add the dried red chili peppers and cook briefly until fragrant, being careful not to burn them.
Add the quartered mushrooms and chopped onion to the wok. Stir-fry until the onions are softened and translucent.
Return the fried chicken to the wok with the mushrooms and onions.
In a separate bowl, prepare the sauce by mixing together the chicken broth, soy sauce, Sichuan hot bean sauce, cayenne pepper, white pepper, and ground Sichuan peppercorns. Add 1 tablespoon of cornstarch to the sauce mixture and stir until well combined.
Pour the sauce over the chicken and vegetables in the wok. Stir-fry briefly until the sauce thickens, coating all the ingredients evenly.
If the sauce becomes too thick, add a little water to reach the desired consistency. The sauce should be fairly dry and cling to the chicken and vegetables.
Serve the Sichuan Chili Chicken hot with steamed rice, if desired. Enjoy!
Note: If grinding your own Sichuan peppercorns, ensure to pass them through a sieve to remove any gritty particles for a smoother texture.
For a lower-fat alternative, you can stir-fry the chicken instead of deep-frying it. While the result will be slightly different, it is still a delicious and acceptable option.