In a bowl, toss the steak strips with cornstarch, salt, and pepper until well coated. Set aside.
Heat oil in a wok or large skillet over high heat. Add the steak strips and stir-fry for 3-4 minutes until crispy and browned. Remove and set aside.
In the same pan, stir-fry the red pepper, broccoli, garlic, and ginger for 2-3 minutes.
In a bowl, mix together the lime juice, dark soy sauce, sugar, and chopped chilies. Pour into the pan with the vegetables and bring to a boil. Simmer for 2-3 minutes until the sauce thickens slightly.
Meanwhile, cook the egg noodles in boiling water according to package instructions until tender. Drain and set aside.
Add the crispy beef, cooked noodles, and spring onion pieces to the pan with the sauce and vegetables. Toss everything together until well combined and heated through.
Serve the sticky beef noodles in bowls, garnished with chili flakes, extra chopped chilies, and spring onions.