In a large skillet/Wok over medium-high heat, brown ground beef until no longer pink.
Drain any fat, then add garlic and cook until gragrant, about 1 minute
In a separate mixing bowl, add soy sauce, beef broth, brown sugar, hoisin sauce, ginger, red pepper flakes and black pepper. Mix well, then add to meat. Stir in to meat mixture.
Using same mixing bowl, dissolve the corn starch with water and then add to sauce.
Stir and bring sauce to a gentle boil.
Once sauce has thickened, add spaghetti and mix in well.
Let noodles sit in sauce 2-3 minutes to absorb some flavor.
You can either serve to plates and then top with green onions or add green onions to mix at last possible minute before you remove from the stove. Personally I did the latter. The onion releases some of it's juices to the mixture, yet remain crispy and firm.