In a bowl, toss the sliced flank steak with cornstarch until well coated. Let it sit for about 10 minutes to absorb the cornstarch.
Heat vegetable oil in a large skillet or wok over medium-high heat. Once hot, add the beef in batches, cooking until crispy and browned, about 3-4 minutes per batch. Remove the beef and drain on paper towels.
In a separate bowl, whisk together soy sauce, honey, rice vinegar, garlic, and ginger. Pour this mixture into the skillet and bring to a simmer.
Cook the sauce for about 2-3 minutes until slightly thickened.
Meanwhile, cook the egg noodles according to package instructions. Drain and set aside.
Add the crispy beef back into the skillet with the sauce, stirring to coat the beef evenly.
Toss the cooked noodles into the skillet, mixing everything together until well combined.
Serve hot, garnished with chopped green onions and sesame seeds if desired.