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 dry with paper towels. Heat oil in a large skillet or Dutch oven over medium-high heat. Add chicken skin-side down and brown for 2-3 minutes per side. Work in batches if necessary to avoid overcrowding.
03 - If using onions, add to the pan and sauté for 2 minutes until softened. Pour in the reserved marinade and water. Add potatoes if desired. Bring the mixture to a gentle simmer.
04 - Cover the pan, reduce heat to low, and cook for 25-30 minutes. Stir occasionally to ensure even cooking. Continue until chicken is tender and reaches an internal temperature of 165°F.
05 - Uncover the pan and simmer for an additional 10-15 minutes. Allow the sauce to reduce and thicken to your preferred consistency. Adjust seasoning if needed and discard bay leaves before serving.
06 - Plate the chicken with sauce over steamed jasmine or white rice. Garnish with chopped scallions or fried garlic if desired. Serve immediately while hot.