Bring a large pot of water to a boil and cook the pasta according to the package instructions. Once cooked, drain and set aside.
In a large skillet set over medium-high heat, cook the ground beef until it is no longer pink, breaking it up as it browns.
Drain excess fat if necessary, then add the minced garlic and sauté for about 1 minute until fragrant.
Stir in the soy sauce, beef broth, brown sugar, hoisin sauce, ground ginger, red pepper flakes (if using), and black pepper until well combined.
In a small bowl, mix the cornstarch with 2 tablespoons of cold water until dissolved, then add it to the skillet with the beef mixture. Stir and bring the sauce to a gentle boil until it thickens.
Add the cooked noodles to the skillet and toss until everything is evenly coated in the sauce.
Let the noodles sit for 2 to 3 minutes to absorb the flavor.
Garnish with sliced green onions and serve hot. Enjoy!