Bring a large pot of water to boil for noodles. Meanwhile, heat a large skillet over medium-high heat and add ground beef. Cook, breaking apart with wooden spoon, until no pink remains, about 5-7 minutes.

Drain excess fat from beef. Add minced garlic and grated ginger to skillet. Cook for 1 minute until fragrant.

In a small bowl, whisk together soy sauce, beef broth, brown sugar, hoisin sauce, black pepper, and red pepper flakes if using.

Pour sauce mixture over beef and stir to combine. In separate bowl, dissolve cornstarch in 2 tablespoons cold water. Add slurry to skillet.

Bring to gentle boil and cook until sauce thickens, about 2-3 minutes. Meanwhile, cook noodles according to package directions until al dente. Drain well.

Add cooked noodles to skillet with beef and sauce. Toss until all noodles are coated. Let sit 2-3 minutes to absorb flavors.

Serve hot, garnished with sliced green onions and sesame seeds.