Whisk together brown sugar, soy sauce, sesame oil, red pepper flakes, and ginger in a small bowl. Set aside.
Heat vegetable oil in a large skillet over medium-high heat.
Add minced garlic and cook for 1 minute until fragrant.
Add ground beef and cook for 3-5 minutes, breaking it apart with a spoon, until browned and cooked through.
Drain excess fat from the skillet.
Stir in the prepared sauce and green onions, then simmer for 2 minutes.
Serve the beef mixture over cooked white rice.
Garnish with additional green onions and sesame seeds before serving.