Place mung bean noodles in a large bowl and cover with boiling water. Let soak for 10 to 15 minutes or until softened. Drain and toss with half a teaspoon of toasted sesame oil to prevent sticking.
Heat a small saucepan or wok, heat the beef stock to a simmer and then keep warm on low heat.
In small frying pan set over medium heat, dry toast the peppercorns until fragrant. Remove from heat and crush in a mortar and pestle or place in a plastic bag and crush with a rolling pin or use a spice grinder.
Heat a wok over high heat and add the peanut oil. Add the garlic, ginger, chili, and one tablespoon of the ground Sichuan peppercorns and stir-fry a few seconds. Add pork and chili bean sauce and continue stir-frying. As the meat browns add rice wine. When meat has browned, add tofu and mix gently. Season the stir fry with soy sauce, black rice vinegar, sesame oil, salt, and ground white pepper.
Add the hot beef stock to the pork and tofu mixture and bring to a boil. In a small bowl, stir together the cornstarch and water, then stir into sauce to thicken. Stir in the scallions and remove from heat. Serve over noodles and sprinkle with remaining Sichuan peppercorns.