In a large bowl, combine the diced chicken with 2 tablespoons of soy sauce, rice vinegar, and cornstarch. Stir to coat evenly. Set aside for ten minutes while you prep the other ingredients.
While the chicken is marinating, cook the udon noodles according to the package directions. Drain and set aside.
In a small bowl, mix the remaining 2 tablespoons of soy sauce, oyster sauce, toasted sesame oil, garlic, and ginger. Stir to combine and set aside.
Heat 1-2 tablespoons of neutral oil in a large, high-sided skillet over medium-high heat. Add the marinated chicken and cook for about three minutes, or until done. Remove it from the skillet and set aside on a plate.
In the same skillet, add more oil if necessary. Toss in the onions and carrots. Cook for about two to three minutes, stirring frequently, until they start to soften.
Add the bok choy and the white parts of the scallions. Cook for an additional two to three minutes, or until all the vegetables are cooked to your liking.
Next, add the cooked noodles to the skillet. Pour the stir fry sauce over everything and toss to combine, ensuring the sauce coats each piece of noodle and vegetable evenly.
Return the cooked chicken to the skillet. Stir fry for about one minute or until everything is heated through.
Taste the stir fry and add additional soy sauce, oyster sauce, or sesame oil if desired. Garnish with sliced chiles or your favorite toppings and serve immediately.
