Cut chicken into small pieces (2-3 inches by 1 inch thick)
Place the chicken and the soy sauce, ketchup, brown sugar, lemon juice, oyster sauce, garlic, ginger, and sesame oil into a gallon-sized zipper bag,
Marinade in the fridge for at least an hour.
Heat a cast-iron skillet and cook the chicken until it's fully cooked 165° and slightly charred, don't overcrowd the pan if using a skillet (you could bake the chicken at 425 degrees on a foil-lined pan if desired)
Serve with rice, rice noodles, and vegetables, as an appetizer, and top the chicken with sesame seeds and cilantro.