Marinate the chicken: Toss the sliced chicken with 1 tablespoon soy sauce and the cornstarch. Let it sit for 10 minutes while you prep the vegetables.

Cook the noodles: Cook the chow mein noodles according to the package directions until just tender. Drain and toss with a drizzle of oil so they don't stick together.

Make the sauce: Whisk together the 3 tablespoons soy sauce, oyster sauce, sesame oil, and sugar in a small bowl. Set aside.

Sear the chicken: Heat 1 tablespoon of the vegetable oil in a large skillet over high heat. Add the chicken in a single layer and sear for 3-4 minutes, until golden and cooked through, 165°F internal. Transfer to a plate.

Stir-fry the vegetables: Add the remaining oil to the pan. Add the cabbage, carrots, garlic, and ginger, and stir-fry for 2-3 minutes, until the cabbage is just wilted but still has some crunch.

Combine: Return the chicken to the pan along with the noodles. Pour in the sauce and toss everything together for 1-2 minutes, until the noodles are evenly coated and heated through.

Finish and serve: Stir in most of the green onions, reserving some for topping, and serve hot.