Combine the brown sugar, soy sauce, oil, pepper flakes, sesame seeds and ginger together in a small bowl. Cook the ground beef and garlic in a pan over medium heat. Making sure you break up the beef as it cooks. Once you have browned the beef add the sauce to the pan. Continue to cook for 5 minutes. Remove the pan for the heat and stir in the green onions. Top some rice with the beef mixture.