Bring water to a boil in a large saucepan over high. Add salt to water and cook noodles according to instructions on the package, until just under al dente, about 2 to 3 minutes. Drain noodles thoroughly in a colander, and rinse under cold
water to stop the cooking process. Drain, lifting noodles to separate and dry the strands. Set aside.
Stir together stock, soy sauce, oyster sauce, and sesame oil in a small bowl. Set aside.
Heat oil in a wok over high until shimmering and fragrant; swirl to coat wok. Add garlic; cook, stirring constantly, until it starts to brown around edges, about 10 seconds. Add mushrooms and cook, stirring constantly, about 30 to 45 seconds.
The mushrooms will soak-up the oil, so add a bit more as needed if they look dry. Add bean sprouts; cook, stirring constantly, until wilted, about 1 minute.
Stir sauce and add to mixture in wok; bring to a boil over high. Add noodles to wok; cook, stirring constantly, until noodles absorb sauce, about 2 minutes. Season with additional soy sauce to taste. Add the green onions and transfer
noodles to a platter.