In a small jar with a tight-fitting lid, combine oil, vinegar, hoisin sauce, soy sauce, ginger, and sesame oil. Shake vigorously until combined.Allow flavors to blend at room temperature while preparing the rest of the salad. Or, refrigerate for up to 4 days.
To make the Salad
In a large bowl, combine the chicken, cabbage, carrots, scallions, and cilantro. Shake the dressing to recombine and pour over the salad. Toss until evenly coated. Sprinkle with chow mein noodles and sesame seeds, if using, right before serving.