Start by placing your large skillet over medium-high heat and adding the ground beef to brown. Let it get a nice sear, breaking it into crumbles, and in the last two minutes of cooking, stir in your fresh minced ginger and garlic so they become fragrant without burning.
While your beef is searing away, get a pot of water boiling and cook your noodles according to the package directions. It is best to cook them just until al dente because they will continue to cook slightly when you toss them into the hot sauce later.
Once the beef is fully cooked and drained of excess grease, return it to the pan and pour in the beef broth, soy sauce, brown sugar, hoisin sauce, black pepper, and red pepper flakes. Stir everything well to combine the flavors with the meat.
Whisk your cornstarch and cold water together in a small cup until smooth, then pour this slurry into the bubbling beef mixture. Stir constantly as you bring it to a low boil; you will see the sauce transform from watery to a rich, glossy glaze within a minute.
Finally, toss your drained noodles directly into the skillet with the thickened beef sauce. Use tongs to gently mix until every strand of pasta is coated in that delicious dark glaze, let it sit for a minute to absorb the flavor, and garnish with green onions.