Finely chop the 120g preserved mustard greens, squeezing out any loose brine with your hands first so they fry rather than steam later. Thinly slice the 4 scallions and roughly crush the 60g roasted peanuts with the flat of a knife or in a bag with a rolling pin, leaving some pieces the size of half a peanut. If the sesame seeds are raw, toast the 2 tbsp in a dry pan over medium heat for 2–3 minutes, shaking often, until golden and fragrant, then tip them out to stop the cooking. Pick the cilantro leaves from their stems. Set everything out in small bowls beside the stove. That complete setup matters because the noodles must be tossed and topped within moments of draining, with no time left to chop anything.

Stir the jar of Chinese sesame paste well first, since the oil separates on standing, then measure 6 tbsp into a mixing bowl (or 4 tbsp sesame paste plus 2 tbsp smooth tahini). Add the 6 tbsp Sichuan chili oil, 4 tbsp light soy sauce, 2 tbsp dark soy sauce, 4 tbsp Chinkiang black vinegar, 2 tsp sugar, 2 tsp roasted ground Sichuan pepper and the 3 grated garlic cloves. Stir until smooth. Heat the stock until steaming, then whisk it in a few tablespoons at a time, using 240ml to start. The paste may seize and thicken at first; keep whisking and it will turn silky. Stop when the sauce is genuinely thick but pourable, like loose yoghurt, and save the remaining stock for later; if using noodle water instead, loosen the sauce partly now and finish it once the noodles are boiling. Taste it: salty, nutty, spicy, slightly tangy and lightly numbing. That gradual loosening is what turns a stiff paste into a glossy sauce that can coat every noodle.

Heat a wok or wide skillet over medium-high heat until hot. Add the 2 tsp neutral oil only if the pork is very lean; ordinary ground pork renders enough fat on its own. Add the 600g ground pork and break it into small crumbles with a spatula. Cook for 5–7 minutes, stirring and pressing it against the pan, until the released moisture has evaporated, the fat begins to render and sizzle, and the crumbles start to brown. If liquid is still pooling, keep cooking with the heat high rather than draining it, so the juices reduce back into the meat. Do not stop at grey, merely cooked pork; real browning is the goal. That patient browning is what concentrates the pork's flavour and builds the crisp edges the finished topping needs.

Push the pork to one side, add the 2 minced garlic cloves and 1 tsp minced ginger to the cleared space and stir-fry for 20–30 seconds, just until fragrant, then mix them through the meat. Add the chopped preserved mustard greens, 1 tbsp light soy sauce, 1 tbsp Shaoxing wine, 1 tsp sugar and ¼ tsp white pepper. Stir-fry for 2–3 minutes more, until the pork is well browned and slightly crisp in spots and the greens have fried into the mixture and smell savoury rather than raw and briny. The topping should look moist but not wet, with no liquid in the base of the wok; if any remains, give it another 30 seconds over the heat. Keep it warm off the heat. That final fry is what removes the greens' raw edge and stops excess liquid from diluting the noodle sauce.

While the pork cooks, bring a large pot of unsalted water to a rolling boil. Add the 600g wheat noodles, stir at once to separate the strands and cook until just tender and springy, about 2–4 minutes for fresh noodles or as the packet directs for dried, tasting a strand 30 seconds before the time is up. Pull them while they still have a slight bite, since they keep softening in the hot sauce. Before draining, scoop out about 250ml of the cooking water and keep it hot. Drain the noodles well, shaking off the excess water, but do not rinse unless your noodle type absolutely requires it. That slight undercooking is what keeps the noodles bouncy and chewy once they meet the sauce.

Give the sauce a quick stir and divide it among 4 warmed serving bowls. If it has thickened while standing, loosen it with some of the remaining hot stock or 1–2 tbsp of the reserved noodle water per bowl, until each bowl holds a loose, glossy layer of sauce at the bottom rather than a stiff paste. Work quickly, so the noodles do not sit in the colander for more than a minute; drained noodles left standing start to clump and lose their surface gloss. Have the pork topping and the prepared garnishes within reach. That loose layer of sauce is what lets the hot noodles absorb it and emulsify it into a coating in the next step.

Divide the hot noodles among the bowls, about 150g in each, and immediately toss them thoroughly in the sauce with chopsticks or tongs, lifting from the bottom, until every strand is evenly coated and glossy. The finished texture should be genuinely glossy, not dry and not soupy; if a bowl looks dry, add another splash of hot noodle water and toss again. Spoon a quarter of the browned pork over each bowl, then scatter over the scallions, crushed peanuts, toasted sesame seeds and a few cilantro leaves. Finish with a little extra Sichuan chili oil, only if needed, so a small amount of red oil pools lightly around the noodles. Serve at once and toss again at the table. That fast toss while the noodles are hot is what lets the sauce emulsify and cling instead of sliding to the bottom.