Whisk the sesame paste with warm water, a tablespoon at a time, until smooth and pourable like heavy cream. Divide among 4 serving bowls.
Add the chili oil with flakes, soy sauce, black vinegar, ground Sichuan pepper, garlic, and sugar to each bowl; whisk briefly.
Heat the oil in a wok over medium-high heat. Spread the ground pork in a thin layer and brown 2-3 minutes undisturbed, then break up and stir-fry about 4 more minutes until crumbly and caramelized. Add the Shaoxing wine, soy sauces, and sugar; cook 1 minute. Keep warm.
In the same pan, stir-fry the chopped preserved mustard greens 1-2 minutes until fragrant and lightly crisped at the edges.
Boil the noodles in salted water until just tender (fresh: ~2 minutes; dried: 5-7). Add the bok choy leaves for the last 60 seconds. Reserve 1 cup of noodle water, then drain.
Loosen each bowl's sauce with a splash of hot noodle water, divide in the noodles, and toss until every strand is glossy. Top with pork, mustard greens, bok choy, scallions, and peanuts. Serve immediately.