Make the noodles: Bring a large pot of salted water to a boil. Add the noodles, stir and cook until al dente, 2 to 4 minutes. Drain, then rinse under cold water and transfer to a bowl. Drizzle with 1 teaspoon sesame oil and toss to coat.
Heat a wok or large skillet over high heat until smoking and add the peanut oil. Add the ginger, chiles and garlic and stir-fry 30 seconds; add the ground beef and cook, breaking up the meat with a spatula, until browned, 2 to 3 minutes.
Combine the tahini and the remaining 1 teaspoon sesame oil in a small bowl. Add the cornichons to the wok. Stir in the tahini mixture, soy sauce, rice wine, vinegar and ground peppercorns; cook until the beef begins to crisp, 2 to 3 more minutes. Season with white pepper and remove from the heat.
Prepare the toppings: Bring the chicken broth to a boil in a medium saucepan over medium heat. Combine the chili oil, sesame oil, soy sauce, ground peppercorns and chiles in a small bowl.
Divide the noodles among bowls and sprinkle the beef mixture evenly over each. Pour the hot broth over the noodles; top with the chili oil mixture, scallions and cilantro.