Begin by making the sauce. In a medium bowl, whisk together Worcestershire sauce, oyster sauce, ketchup, soy sauce, and brown sugar until smooth and fully combined. Set aside to let the flavors meld.

Prepare the noodles by removing them from the packaging and placing them in a colander. Rinse thoroughly under cold water while gently separating the strands with your fingers to loosen and untangle. Drain well and set aside.

Heat the peanut oil in a large wok or skillet over medium-high heat. Once hot, add the sliced chicken breast and stir-fry until the pieces are cooked through and no longer pink, about 4 to 5 minutes.

Add the sliced onion and julienned carrots to the pan. Stir-fry for another 2 minutes until the onion turns slightly translucent and the carrots begin to soften. Stir in the shiitake mushrooms, cabbage, and green onions. Toss everything together and continue to cook for another minute to blend the textures and flavors.

Add the prepared yakisoba noodles to the wok. Pour the sauce mixture over the top, then toss everything together using tongs or chopsticks, ensuring the noodles are evenly coated and the vegetables and chicken are well distributed.

Continue to stir-fry for an additional 2 minutes until the noodles are heated through and everything is piping hot.

Serve immediately, with sriracha or your favorite chili sauce on the side if desired.