Cook noodles according to package instructions. Drain and set aside.
In a large skillet or wok, heat sesame oil over medium heat. Add ground beef and cook until browned, about 6–7 minutes. Drain excess fat.
Stir in garlic, ginger, and green onions. Sauté for 1 minute until fragrant.
In a small bowl, mix soy sauce, brown sugar, hoisin sauce, and red pepper flakes. Pour into the beef mixture and simmer for 2–3 minutes.
Stir in the cornstarch slurry and cook until the sauce thickens, about 1–2 minutes.
Add cooked noodles and toss to coat in the sauce.
Serve hot, topped with more green onions and sesame seeds if desired.
