Heat vegetable oil in a skillet over medium-high heat. Add chopped onion and minced garlic, cooking until softened, about 4-5 minutes.

Add ground beef to the skillet, breaking it apart with a spoon. Cook until browned and fully cooked through.

In a small bowl, whisk together soy sauce, brown sugar, sesame oil, ground ginger, and red pepper flakes.

Pour the sauce over the cooked beef and stir well. Let it simmer for 3-4 minutes to allow the flavors to meld.

Serve the beef mixture over a bed of cooked white rice. Garnish with sliced green onions and sesame seeds for a finishing touch.