In a bowl, toss the sliced beef with cornstarch until evenly coated. Set aside.
In a separate small bowl, whisk together the soy sauce, dark soy sauce, brown sugar, sesame oil, and rice vinegar to make the sticky sauce.
Cook the egg noodles according to the package instructions until al dente. Drain, rinse under cold water to stop the cooking process, and set aside.
Heat 1 tablespoon of vegetable oil in a large wok or skillet over high heat. Add the coated beef strips in a single layer and sear for 2 to 3 minutes until browned and crispy. Remove the beef from the pan and set aside.
In the same skillet, heat the remaining tablespoon of oil over medium-high heat. Add the minced garlic, grated ginger, and chopped green onions, sautéing for 30 seconds until fragrant.
Pour the prepared sticky sauce into the skillet and let it simmer for 1 to 2 minutes until it begins to bubble and thicken.
Return the cooked beef to the skillet, along with the cooked egg noodles. Toss everything together continuously for 1 to 2 minutes until the noodles and beef are thoroughly coated in the sauce and heated through.
Serve immediately, garnished with the reserved green onions and a sprinkle of sesame seeds.