Heat vegetable oil in a large, deep skillet or Dutch oven over medium-high heat. Season the chicken thighs with salt and pepper, then place them skin side down in the hot oil. Flip and cook the other side until it turns a little brown. Remove the chicken from the skillet and set aside. It won’t be cooked at this stage, just a nicely caramelised exterior.
In the same skillet, reduce the heat to medium and add the grated onion and celery to the pan juices and stir, cooking for a few minutes until softened and fragrant. Stir in Lee Kum Kee Minced Garlic and ginger and cook for an additional minute or so until fragrant.
Return the browned chicken thighs to the skillet, skin side up, on top of the onion and celery mixture and remove from heat.
Whisk together Lee Kum Kee Hoisin Sauce, Lee Kum Kee Char Siu Sauce, Lee Kum Kee Premium Soy Sauce, and rice vinegar, then pour the mixture over the chicken thighs currently resting in the skillet. Add enough chicken broth or water to partially submerge the chicken thighs.
On a medium heat, bring the mixture to a simmer, then reduce the heat to low. Cover the skillet and let the chicken braise for around 25-30 minutes, or until the chicken is tender and fully cooked. Once the chicken is done, remove it from the skillet and set it aside. Increase the heat to medium-high and let the sauce simmer until it thickens and reduces a little. Keep stirring so it doesn’t stick.