Soak the dried mung bean noodles in water for 10 minutes. You can do this while you prep your other ingredients. Drain and set aside.
Heat a wok over medium-high heat until it’s just starting to smoke. Reduce the heat to low, and add the oil and minced ginger. Cook the ginger for 30 seconds to 1 minute, watching it closely to prevent burning.
Increase the heat to high, and add the firm tofu. Quickly spread the tofu in a single layer in the wok, and let it brown. Do not disturb the tofu until it forms a crust and pulls away from the surface of the wok. Once golden brown on one side, stir-fry the tofu cubes until golden on most sides and infused with ginger flavor.
Add the garlic, and cook for 30 seconds. Next, clear a space in the center of the wok. Add the spicy bean sauce and fry it for another 30 seconds.
Add the stock (or water and mushroom powder), chili oil, sugar, light soy sauce, and dark soy sauce. Bring everything to a boil.
Once boiling, add the glass noodles and scallions. Stir everything together for 1-2 minutes. It will look soupy, but after a few minutes, the noodles should have mostly absorbed the liquid. Serve alone, or with steamed rice!