0.25 cup roasted peanuts – coarsely chopped (for serving)
Instructions
Bring a large pot of water to a boil for the noodles.
Heat the neutral oil in a skillet over medium-high heat. Add the ground pork and cook, breaking it up, until it loses its pink color, 3–4 minutes. Add the ginger and the Shaoxing wine and stir-fry until the pork is browned with some crisp edges, 2–3 minutes more. Add the Sichuan preserved mustard stem (ya cai) and stir-fry until very fragrant, 1–2 minutes. Transfer the pork mixture to a bowl and keep warm.
Salt the boiling water lightly, add the dried thin wheat noodles, and cook until just tender but springy, 2–4 minutes depending on thickness. Reserve 0.75 cup of the hot noodle water, then drain the noodles well.
In a large mixing bowl, whisk the Chinese sesame paste, light soy sauce, Chinese black vinegar, Sichuan chili oil with sediment, and garlic until smooth. In a small dry skillet over medium heat, toast the Sichuan peppercorns until fragrant, 1–2 minutes; grind to a fine powder and whisk into the bowl. Gradually whisk in enough of the reserved hot noodle water (about 0.5–0.75 cup) until the sauce is the consistency of heavy cream.
Add the drained noodles to the bowl and toss until evenly coated, 30–60 seconds. Divide among bowls, spoon the pork and ya cai mixture over the top, and finish with the scallions and roasted peanuts. Serve immediately while hot and slick with sauce.