Prep the toppings. In a medium frying pan, add a tablespoon of oil (preferably peanut but vegetable or canola also work) and saute the yacai for a minute or two. Remove and set aside. Then, in the same pan, heat 2 more tablespoons of oil.
To the frying pan you were just using, add a tablespoon of oil and then add the ground pork, the dark soy sauce, the light soy sauce, the ground white pepper, the sugar, and the Sichuan peppercorn powder and msg, if using. Stir fry until cooked through, and break up with a spatula into small bits. Once cooked, remove from heat and set aside.
Then, make the noodles. Bring a large pot of water to a boil. Cook the noodles according to the package instructions. Remove the noodles with chopsticks or tongs and into a bowl. When you use Chinese-style wheat noodles, you NEED to rinse them in cold water upon removing them from the cooking water. This a) stops the cooking process and b) keeps them from clumping up into one giant ball of pasta. Reserve the water to blanche your bok choy or other green of choice.
While the water is heating, prepare the sauce in each individual serving bowl (except, of course, the pasta water, which you can add before removing the cooked noodles from the water).
Blanche the bok choy. After you remove the noodles from the pot of water, add pasta water to the bowls, then blanch Shanghai bok choy in the pasta water for a few seconds, until a deeper shade of green. Remove, set aside.
Layer noodles in bowl, and top with minced pork, ya cai, chopped green onions, bok choy (or other green), and crushed crushed peanuts and toasted sesame seeds.
To eat, use your chopsticks to fold sauce and ingredients into your bowl of noodles. Optionally, you can set Chinese black vinegar and more chili oil out on the table to let people season to taste. Enjoy! 慢慢吃!