Heat a wok over high heat and add the oil. When the oil starts to smoke, add the garlic, ginger and chiles, and stir-fry for a few seconds. Then, add the fermented black beans and stir quickly. Add the beef slices and stir-fry for 1 minute, keeping the ingredients moving in the wok. As the meat starts to brown, add the rice wine. Add the green peppers and stir-fry for 1 minute, and then add the stock and bring to a boil. Season the stir-fry with the soy sauces. Combine the cornstarch and 2 tablespoons cold water, add to the wok and stir to thicken. Add the ho fun noodles, breaking them up with a spoon and stirring everything together. Garnish with the sliced scallions and serve.
If using dried ho fun noodles, cover them with boiling water in a medium bowl and soak for 10 to 15 minutes to loosen and soften.