In a small bowl, whisk together Worcestershire sauce, soy sauce, ketchup, oyster sauce (if using), and sugar until well combined.

If using instant yakisoba noodles, soak them in warm water for 1-2 minutes until they loosen and separate.

Preheat a large skillet or wok over medium-high heat until faint smoke rises.

Add a tablespoon of vegetable oil to the hot skillet, followed by the sliced onions and julienned carrots. Stir-fry for 2-3 minutes.

Incorporate the shredded cabbage into the skillet, stirring together for another 2-3 minutes.

Add in the soaked yakisoba noodles and pour the prepared sauce over the mixture, gently tossing everything together.

Stir in most of the sliced green onions, reserving some for garnish. Continue cooking for another minute.

Transfer the yakisoba to serving bowls and garnish with reserved green onions and optional toppings.