Once the noodles are soaked and drained, heat your wok over medium-high heat. Add 1 tablespoon of grapeseed oil.
1 tablespoon grapeseed oil
Add the red onion and garlic, sautéing for 1–2 minutes until fragrant and lightly browned.
Pour the sauce into the wok and taste again—this is the final chance to adjust the balance of sweet, salty, sour, and spicy. See notes on how to get these flavors.
Add the crispy mushrooms and bring the sauce to a boil.
Add the noodles to the wok and stir-fry for 2–5 minutes, until the sauce is mostly absorbed. Taste a noodle to check for doneness. If the noodles seem dry, add water 1 tablespoon at a time.
Once fully cooked, turn off the heat and fold in the mung bean sprouts and green onions. Let the noodles sit for a couple of minutes to allow the veggies to soften slightly from the residual heat.
Give everything one last stir to combine. Serve hot, garnished with crushed peanuts and lime wedges.