Saute ground beef. Add garlic & saute 30 seconds. Drain grease.
Add ginger, brown sugar, soy sauce, hoisin, broth, vinegar, and pepper flakes.
Make slurry with cornstarch and cold water. Pour over beef mixture and stir thoroughly.
Cook until thickened, ~3 min. Stir in cooked spaghetti and cook 2 min more.