Place the noodles in a large bowl and cover with boiling water. Let soak until softened, 10 to 15 minutes. Drain and toss with 1/2 teaspoon toasted sesame oil to prevent sticking.
In a small saucepan or wok, heat the beef stock to a simmer and then keep warm on low heat.
In a small frying pan set over medium heat, dry-toast the peppercorns until fragrant. Remove from the heat and crush in a mortar and pestle, 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 1 tablespoon of the ground peppercorns and stir-fry a few seconds. Add the pork and chili bean sauce and continue stir-frying. As the pork browns, add the rice wine. When the pork has browned, add the tofu and mix gently. Season the stir-fry with soy sauce, black rice vinegar, the remaining 1 teaspoon sesame oil, salt and ground white pepper.
Add the hot beef stock to the pork and tofu and bring to a boil. In a small bowl, stir together the cornstarch and 2 tablespoons water, then stir into the sauce to thicken. Stir in the scallions and remove from the heat. Serve over the noodles and sprinkle with the remaining peppercorns.
Recipe courtesy of Ching-He Huang, 2011