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 up to overnight in the refrigerator for deeper flavor penetration.
02 - Remove chicken from the marinade and reserve the liquid. Pat chicken pieces completely dry using 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 the pan.
04 - Add sliced onion to the pan and sauté for approximately 2 minutes until slightly softened and fragrant.
05 - Pour in the reserved marinade along with the water. Add quartered potatoes if desired. Bring the mixture to a gentle simmer, stirring to combine.
06 - Cover the pan and reduce heat to low. Cook for 25-30 minutes, stirring occasionally, until chicken is fork-tender and cooked through to an internal temperature of 165°F.
07 - Uncover the pan and continue simmering for 10-15 minutes to reduce the liquid until the sauce reaches your desired consistency. The sauce should coat the back of a spoon.
08 - Discard the bay leaves and adjust seasoning if needed. Serve immediately over steamed white rice, garnished with chopped scallions or crispy fried garlic.