Make the stir-fry: Cook the noodles according to the package instructions. Reserve 1 cup of the noodle cooking liquid, then drain the noodles into a colander. Rinse briefly under cold water to stop the noodles cooking. Shake the colander to release excess liquid, then set aside.
While the noodles cook, in a medium bowl place the pork, cornstarch, salt , and pepper. Toss to coat.
Heat a large nonstick skillet or wok over medium-high heat. Add 1 tablespoon of the oil. Once the oil is hot, add the pork and sauté until lightly browned on all sides, stirring occasionally, until it is cooked through and no longer pink in the center, about 5 minutes. Transfer the pork to a plate or bowl. Set aside.
To the skillet, add the remaining 1 tablespoon oil. Once the oil is hot, add the broccoli, mushrooms, and red onion. Sauté for 8 to 10 minutes, stirring occasionally, until the broccoli is crisp-tender and the mushrooms soften.
Make the sauce: While the vegetables cook, in a small bowl or large liquid measuring cup whisk together the sauce ingredients until combined: the soy sauce, cornstarch, honey, vinegar, pepper, garlic and ginger.
Once the vegetables have cooked, add the pork, sauce, and noodles to the pan. With a pair of tongs, toss to combine the ingredients and evenly coat the noodles with the sauce, adding a little of the reserved noodle cooking liquid as needed if the noodles are sticking together. Continue cooking and tossing for 1 to 2 minutes, until the sauce has thickened and noodles are warmed through. Taste and season with the additional soy sauce and pepper as desired. Remove from the heat, sprinkle with the green onions and sesame seeds, and serve immediately.