Mix the soya sauce, brown sugar, sesame oil, garlic, ginger, and rice vinegar together to make the sauce.
Heat a large skillet to medium heat, and then add the ground beef. Brown the beef while stirring occasionally and breaking up the beef with the back of a spoon.
When the beef has browned, add the green onions and sauce to the skillet, then cook while stirring occasionally until the sauce has thickened.