Prep noodles: Cook the noodles according to package directions until al dente. Drain and set aside.

Make the sauce: In a small bowl, whisk together soy sauce, brown sugar, hoisin sauce, optional heat (Sriracha/red chili), cornstarch, and water (or broth). Stir until smooth; set aside.

Cook aromatics: Heat vegetable oil over medium-high heat in a large skillet or wok. Add minced garlic, grated ginger, and the white parts of green onions. Sauté until fragrant, about 30 seconds.

Brown the beef: Add ground beef, breaking it up with a spatula. Cook until no longer pink and beginning to brown.

Add the sauce: Pour in the prepared sauce. Stir and bring to a simmer. Let it cook for about 2–3 minutes, until the sauce thickens and coats the meat.

Combine with noodles: Add the cooked noodles into the pan, tossing gently to coat them evenly in the sauce.

Finish & season: Drizzle sesame oil, stir through, then sprinkle the green onion greens. Taste and adjust seasoning—add more soy for salt, brown sugar for sweetness, or Sriracha for heat.

Serve immediately, optionally garnished with sesame seeds or extra green onions.