Toss the sliced sirloin steak with cornstarch, salt, and black pepper in a large bowl.
Heat 1 tablespoon of vegetable oil in a skillet or wok over medium-high heat. Add the steak slices and stir-fry for 2–3 minutes until browned and crispy. Remove and set aside.
Add the remaining 1 tablespoon of oil to the skillet and stir-fry the red bell pepper and broccoli florets for 3–4 minutes until slightly softened.
Stir in the minced garlic and ginger, cooking for about 1 minute until fragrant.
In a small bowl, whisk together lime juice, soy sauce, and sugar until the sugar dissolves.
Return the cooked steak to the skillet, pour the sauce over the beef and vegetables, and add the chopped chilies and spring onions. Stir well to coat everything evenly.
Add the fresh egg noodles and toss until thoroughly coated and heated through.
Garnish with chili flakes, chopped chilies, and spring onions before serving.
