In a medium bowl, combine the sliced beef with soy sauce, cornstarch, sesame oil, ground ginger, and black pepper. Mix well and let it marinate for at least 15 minutes.

While the beef is marinating, whisk together all the sauce ingredients in a separate bowl: soy sauce, brown sugar, rice vinegar, cornstarch, honey, sesame oil, sriracha (if using), minced garlic, ground ginger, and water. Make sure there are no lumps of cornstarch.

Cook the noodles according to the package directions. Drain well and set aside. Toss with a little sesame oil to prevent sticking.

Heat a large skillet or wok over high heat. Add a tablespoon of oil. Once the oil is hot, add the marinated beef in a single layer (work in batches if necessary).

Sear the beef for 2-3 minutes per side, until browned and cooked through. Remove the beef from the skillet and set aside.

Add the prepared sauce to the same skillet. Bring to a simmer over medium heat, stirring constantly. Cook for 2-3 minutes, or until the sauce has thickened and become glossy.

Add the cooked beef and noodles to the skillet with the sauce. Toss everything together until the beef and noodles are evenly coated in the sticky sauce.

Serve immediately, garnished with sesame seeds, chopped green onions, and red pepper flakes (if desired).