Using a sharp knife, cut the pork tenderloin in half lengthwise then cut it crosswise into thin slices.
In a large bowl, mix the pork with the soy sauce, cornstarch, black pepper and a pinch of salt. Let stand for 15 minutes.
Heat a large skillet over high heat. Add 2 tablespoons of the vegetable oil and swirl to coat the pan. Add the pork and spread it into an even layer. Cook the pork, undisturbed, until it is browned on the bottom, 3 to 5 minutes, then continue cooking the pork while stirring for an additional 2 minutes. Using a slotted spoon, transfer the pork to a plate.
Add the remaining 1 tablespoon of vegetable oil to the pan and red the heat to medium-high. Add the asparagus and a pinch of salt and cook, stirring, until the asparagus is crisp-tender, about 3 minutes.
Return the pork to the pan and cook, stirring, until hot, about 1 minute.
Serve the pork garnished with sliced scallions and sesame seeds.