Cook the egg noodles according to package instructions, drain, and set aside.
In a mixing bowl, combine sliced flank steak with soy sauce, oyster sauce, hoisin sauce, sesame oil, and brown sugar. Let marinate for about 15 minutes for enhanced flavor.
In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the marinated flank steak in a single layer and cook for about 2-3 minutes on each side until browned. Remove the beef from the pan and set aside.
In the same skillet, add minced garlic and grated ginger. Sauté for 30 seconds until fragrant.
Add the julienned bell pepper and chopped bok choy to the skillet. Stir-fry for about 3-4 minutes until the vegetables are tender yet crisp.
Return the cooked beef to the skillet with the vegetables. Add the cooked egg noodles and toss everything together. Cook for an additional 2-3 minutes, allowing the flavors to meld.
Season with salt, black pepper, and crushed red pepper flakes to taste.
Remove from heat and sprinkle with chopped scallions before serving.
Notes
Serve in deep bowls and garnish with additional scallions and a sprinkle of crushed red pepper flakes for an extra kick.