Par-boil 180 g dried chow mein noodles according to package instructions — usually around 3-4 minutes. Drain.
Mix the sauce in a small bowl. Whisk together 1 tablespoon light soy sauce, 1 tablespoon dark soy sauce, ½ tablespoon vegan oyster sauce/stir-fry sauce, ¾ teaspoon sugar, and 1 small pinch salt. Be wary of the salt, since soy sauce is also high in sodium.
Heat a large wok over high heat and add 1 teaspoon neutral oil. Once it smokes, add 40 g white onion (sliced) and 100 g beansprouts. Stir-fry for 30 seconds, then add the cooked noodles. Mix well.
Add the sauce to the wok and toss everything together.
Garnish with 1 spring onion (or Chinese chives) and serve.