Heat vegetable oil in a large skillet over medium high heat. Add garlic and cook, stirring constantly, until fragrant, about 1 minute. Add ground beef and cook until browned, about 3-5 minutes, making sure to crumble the beef as it cooks; drain excess fat.
In a small bowl, whisk together brown sugar, soy sauce, sesame oil, red pepper flakes and ginger.
Serve immediately, garnished with green onion and sesame seeds, if desired.
Stir in soy sauce mixture and green onions until well combined, allowing to simmer until heated through, about 2 minutes.