01 - Combine chicken, soy sauce, vinegar, garlic, bay leaves, peppercorns, and brown sugar in a large bowl. Toss to coat thoroughly. Marinate for at least 30 minutes, or refrigerate overnight for deeper flavor penetration.
02 - Remove chicken from marinade and reserve the liquid. Pat chicken pieces completely dry with paper towels to ensure proper browning.
03 - Heat vegetable oil in a large deep skillet or Dutch oven over medium-high heat. Add chicken pieces skin side down and brown for 2-3 minutes per side. Work in batches if necessary to avoid overcrowding.
04 - Add sliced onion to the pan and sauté for 2 minutes until slightly softened and fragrant.
05 - Pour in the reserved marinade and water. Add quartered potatoes. Bring mixture to a simmer, stirring to combine.
06 - Cover the pan, reduce heat to low, and cook for 25-30 minutes. Stir occasionally until chicken is fork-tender and cooked through completely.
07 - Uncover the pan and continue simmering for 10-15 minutes. Allow sauce to reduce and thicken to desired consistency while spooning sauce over chicken.
08 - Discard bay leaves and adjust seasoning if needed. Serve immediately over steamed rice, garnished with chopped scallions or fried garlic.