1 lb fresh Chinese egg noodles (or use dry spaghetti)
2 tsp peanut or canola oil
4-5 scallions, chopped (set aside 2 Tbsp)
1 clove garlic, peeled, sliced thin
1/2 cup sliced button or shiitake mushrooms, stems removed
1/2 cup Cantonese 3-2-1 sauce (3 parts reduced-sodium soy sauce, 2 parts oyster sauce, 1 part sesame oil), or more as needed
3/4 lb large shrimp (31-40 per-pound size)
2 cups mung bean sprouts (optional), rinsed under cold water
Bring 6 quarts of water to a boil; cook egg noodles over high heat until they float to the surface, then reduce heat and cook for 2-3 minutes until al dente (or cook spaghetti according to package directions). Do not cook all the way through; the noodles will finish cooking in the sauce. Drain, but do not rinse, and reserve the cooking water.
In a large wok or frying pan, heat the oil. Add the scallions and stir fry for 1 minute. Add the garlic and mushrooms, and stir for 1 minute. Add the Cantonese 3-2-1, plus 1-2 tablespoons of the reserved cooking water, then add the shrimp and cook for 2 minutes, until they just begin to turn pink and curl. Add the cooked noodles and the bean sprouts, and stir thoroughly and constantly for 2-3 minutes, turning the noodles over and over, until the ingredients are combined and the sauce is absorbed into the noodles. If needed, add more soy sauce and oyster sauce, to taste. Serve hot or at room temperature.