In a small bowl, whisk together Worcestershire sauce, soy sauce, oyster sauce, ketchup, mirin, sugar, and sesame oil. Set aside.
Cook the Chicken
Heat 1 tbsp of vegetable oil in a large skillet or wok over medium-high heat. Add the sliced chicken thighs and cook for about 4-5 minutes until browned and cooked through. Remove from the pan and set aside.
Stir-Fry the Vegetables
In the same pan, add another tablespoon of oil. Toss in the sliced onion, cabbage, carrot, and bean sprouts. Stir-fry for 3-4 minutes until the vegetables start to soften but still have a bit of crunch. Add minced garlic and ginger, then stir for another 30 seconds.
Add the Noodles
If using pre-cooked yakisoba noodles, rinse them under warm water to loosen. Add them to the skillet, tossing with the vegetables. Pour in the yakisoba sauce and mix well to coat everything evenly.
Combine and Serve
Return the cooked chicken to the pan, mixing it in with the noodles and veggies. Stir-fry everything together for another minute until well combined. Adjust seasoning with salt and pepper if needed.
Garnish and Enjoy
Plate the yakisoba and top with sliced green onions, sesame seeds, and a sprinkle of aonori if desired. Serve with pickled ginger on the side for a classic Japanese touch.