Begin by boiling a large pot of salted water. Once it reaches a rolling boil, add the linguine and cook according to package instructions until al dente, typically around 8-10 minutes. Drain the pasta well in a colander and set it aside.

In a large skillet, heat over medium heat. Add the ground beef, using a spatula to break it apart as it cooks. Stir occasionally, browning the beef thoroughly for about 5-7 minutes until it's no longer pink. Once cooked, drain any excess fat.

Next, stir in the minced garlic with the browned beef, allowing it to cook for about 1 minute until fragrant. This step enhances the overall flavor profile.

In the skillet, add the brown sugar, beef broth, soy sauce, hoisin sauce, ground ginger, black pepper, and red pepper flakes if using. Stir well to combine and let the sauce simmer for about 3-5 minutes.

In a small bowl, mix cornstarch with water to create a slurry. Gradually pour this mixture into the skillet, stirring constantly as the sauce begins to thicken for an additional 2-3 minutes.

Add the drained linguine into the skillet, tossing it gently with the sauce and beef until every strand is generously coated. Let it sauté together for about 1-2 minutes.

Serve your warming Mongolian Ground Beef Noodles hot, garnishing each plate with fresh, sliced green onions.