Begin by separating the Napa cabbage leaves and slicing them diagonally into bite-size pieces.
In a small bowl, combine the black rice vinegar, light soy sauce, optional dark soy sauce, starch, salt, sugar, and water; mix thoroughly and let it rest.
Heat a wok on high until it starts to smoke, then add cooking oil followed by garlic and dried chilies; stir quickly until aromatic but not burnt.
Add the chopped cabbage to the wok, stir-frying until the leafy green parts soften while the white stems remain crisp.
Give the prepared sauce a final stir and pour it over the cabbage in the wok; toss in the scallions and mix well.
Continue cooking just until the sauce thickens and coats the cabbage evenly, then immediately remove from the heat and serve.
