01 - Combine chicken pieces with fish sauce, soy sauce, brown sugar, black pepper, garlic, and shallot in a large bowl. Mix thoroughly to coat all pieces. Marinate for 15 minutes minimum, up to 1 hour for deeper flavor penetration.
02 - Heat oil in a large skillet or clay pot over medium heat. Add 2 tablespoons brown sugar and cook, stirring constantly, until sugar melts and transforms to deep amber caramel. This takes approximately 2-3 minutes—watch carefully to prevent burning.
03 - Add marinated chicken to the caramelized sugar, reserving excess marinade in the bowl. Sear chicken for 3-4 minutes, turning pieces to coat evenly in the caramel and develop golden-brown color on all sides.
04 - Pour in the reserved marinade, water, fish sauce, soy sauce, and sliced chilies if using. Stir thoroughly to combine all ingredients and dissolve any caramelized bits from the pan bottom.
05 - Reduce heat to low, cover, and simmer for 25-30 minutes. Stir occasionally to ensure even cooking. Continue until chicken is completely cooked through and sauce has thickened to a glossy consistency.
06 - Remove the lid during the final 5 minutes of cooking. This allows excess liquid to evaporate and further concentrates the sauce for a rich, coating consistency.
07 - Transfer to a serving dish and top with sliced scallions and fresh cilantro leaves. Serve immediately while hot, accompanied by steamed jasmine rice.