For the meat sauce: Soak the shiitake mushrooms in warm water until they’re soft. Pre-sliced dried shiitakes will take just 30 minutes to reconstitute, while whole shiitakes take longer. Squeeze out the water and roughly chop the mushrooms. Save the mushroom water for the sauce.
Heat a large pan with canola oil. Add chopped onion and sauté over medium heat for a couple of minutes. Add garlic, ginger, green onions, star anise, and shiitakes. Continue to sauté for a minute, until fragrant. Push the vegetables to the sides of the pan, and add the ground pork. Break down the pork and sauté until the meat is all browned, stirring and pushing the meat around constantly.
Add the Shaoxing cooking wine to the pan, and let it cook off for a minute. Add the sauces (soy sauce, tianmianjian, hoisin sauce) and stir to combine. Start with a small amount of tianmianjian and adjust to taste. Add 1/2 cup of the reserved mushroom water (or water if you’re not using dried mushrooms). Turn the heat down to low, and cover the pan. Let simmer for 30 minutes, stirring every so often. As the sauce dries, add more mushroom water. The sauce should be the consistency of a pasta sauce. Taste the sauce as it cooks, adjusting the flavor to your liking. After 30 minutes of simmering, the sauce is almost ready. You can let it cook for even longer (up to an hour on low heat) for a more broken down sauce. Finally, mix the cornstarch with 2 tablespoons cold water and add to the sauce. Stir over low heat for a minute to let the starch thicken the sauce. Stir in 1 tablespoon of sesame oil.
For the noodles: Bring a large pot of lightly salted water to boil. Place half the package of noodles in the pot (unless you have a huge pot, cook the noodles in batches so they took faster). If you let the noodles sit in hot water that takes forever to boil, they will get soggy. Cook the noodles according to the package directions, tasting them as they cook, as you would pasta. I like to take the noodles out while they’re just undercooked, because they will continue to cook a bit as you assemble the dish. The noodles should be dense and chewy.
For the garnish: Julienne the Persian cucumbers. I prefer Persian cucumbers because they’re sweet and crisp, with a light yellow-green colored flesh. They are the perfect complement to the flavor-heavy sauce and chewy noodles. Restaurants usually just garnish the noodles with cucumber, but at home, I try to squeeze in as much veggies as I can into meals. I like to top each bowl off with half of a julienne cucumber or more.
For serving: In each bowl, place approximately 1 cup of cooked noodles. Top noodles with 1/2 cup of sauce and half of a julienned Persian cucumber. Drizzle with a few drops of sesame oil, and serve immediately.