Cook spaghetti noodles according to package instructions. Drain and set aside.
While noodles are cooking, cook ground beef in a large skillet over medium heat, breaking meat into small crumbles with a wooden spatula as it cooks. Drain off excess fat.
Add minced garlic and ginger to the pan and cook, stirring constantly, until fragrant, about 1 minute.
Add soy sauce and beef broth to the skillet, stir to combine.
Add brown sugar, stir to combine.
Add hoisin sauce, stir to combine.
Add red pepper flakes and black pepper. Stir to combine and bring mixture to a simmer.
In a small bowl stir together water and cornstarch to make a slurry.
Add the corn starch slurry to the pan with the beef and continue to cook until the sauce thickens and turns glossy.
Add the cooked spaghetti noodles and toss them with the beef mixture to coat them with the sauce.
Serve immediately garnished with a sprinkle of sliced green onions.