Whisk together soy sauce, hoisin, beef broth, brown sugar, sesame oil, red pepper flakes, and black pepper. In a separate small bowl dissolve cornstarch in cold water. Set both aside.

Boil noodles 1-2 minutes less than package directions. Drain but do not rinse. Set aside.

Heat oil in a large skillet over medium-high heat. Add ground beef, break into crumbles, and cook until well browned with no pink remaining, about 5-6 minutes. Drain excess fat.

Push beef to one side. Add garlic and ginger to the empty space and cook 60-90 seconds until fragrant. Stir into the beef.

Pour sauce over the beef and stir to combine. Bring to a gentle simmer, then stir in the cornstarch slurry. Cook 2-3 minutes until the sauce thickens and coats everything in a glossy layer.

Add drained noodles and toss with tongs until fully coated. Cook together 1-2 more minutes. Taste and adjust seasoning.

Serve immediately topped with sliced green onions and toasted sesame seeds.