In a large bowl, combine 1 tablespoon of the light soy sauce with the cornstarch, Shaoxing wine, and sugar. Add the pork and mix until the pork is thoroughly coated.
In a small bowl, combine the remaining 1 tablespoon light soy sauce with the dark soy sauce, hoisin sauce, chicken stock, and sesame oil.
Fill a large bowl with hot tap water and add the noodles. Let soak until loosened and warmed through, 30 seconds to 1 minute. Drain and set aside. (If using frozen udon, soak them until defrosted, 2 to 3 minutes.)
Heat a large wok or skillet over medium heat. When the wok starts to smoke, add the oil and swirl until shimmery. Add the pork with its marinade and cook, stirring occasionally, until it is golden brown and crispy, 3 to 5 minutes.
Add the kale and toss to combine. When the kale has wilted slightly, add the noodles and the sauce. Crank the heat to high and toss to combine. Sear until everything is smoky and slightly charred, about 2 minutes.
Serve hot with sliced scallions, crispy fried onions, and/or chili oil, if desired.
Notes
Double the sauce--This recipe makes a noodle dish that's lightly coated with sauce. If you prefer saucier noodles, double the sauce.
Sticky noodles--If your noodles are clumping or sticking together after soaking, give them a quick rinse with cold water before setting them aside.
Storage and reheating--Leftover noodles can be stored in a sealed container for up to 3 days. To reheat, warm in a skillet over medium heat until warmed through, adding water or chicken broth as needed to loosen the noodles.