If using dried yuba, rehydrate to package instructions or soak in warm water for 10 minutes completely submerged. Strain and set aside.
To a pot, add water, potatoes, and salt. Bring to a boil, and boil the potatoes just a little under fork tender. Strain the potatoes, and set aside to cool.
To the pot with boiling water, add mushrooms and blanch for 1-2 minutes. Strain and set aside.
Next add the yuba (bean curd) sticks and boil for 2-3 minutes. Strain and set aside. Discard the water.
To a wok over medium heat, add oil and allow it to heat up.
Add scallions, garlic, and ginger and sauté for 1-2 minutes.
Add the mushrooms and sauté for 1 minutes.
Add the potatoes and yuba sticks and stir to combine.
Add the light soy sauce, dark soy sauce, sugar, salt, and vegetable broth. Stir to combine, cover with lid, and simmer for 5 minutes.
Add corn starch slurry, and stir continuously to allow the sauce to thicken to a velvety consistency.
Garnish with scallion greens and serve with steamed brown rice and bok choy.