Bring a large pot of salted water to a boil. Add the noodles and cook according to package instructions until al dente. Drain and set aside.

In a small bowl, whisk together soy sauce, hoisin sauce, beef broth, brown sugar, and crushed red pepper flakes (if using). Set the sauce aside.

Heat the vegetable oil in a large skillet over medium-high heat. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks. Drain any excess fat.

Reduce the heat to medium. Stir in the minced garlic and ginger, cooking for 1 minute until fragrant.

Pour the prepared sauce into the skillet with the cooked beef. Stir well to combine, and let it simmer for 2-3 minutes until the sauce slightly thickens.

Add the cooked noodles to the skillet, tossing to coat them evenly with the beef and sauce mixture. Cook for an additional 2 minutes to heat through.

Transfer to serving plates. Garnish with sliced green onions and sesame seeds. Enjoy hot!