Preheat large skillet over medium-high heat. Add in beef and break apart as it browns with a wooden spoon. Once the beef is completely cooked, pour into a colander, and drain any excess fat off of the meat. Place meat back into the pan.
Reduce heat to medium and add in soy sauce, maple syrup, minced garlic, ginger, red pepper flakes and sesame oil. Cook about five minutes or until the soy sauce reduced slightly. Taste and adjust seasonings with salt and pepper. If meat mixture is getting dry, splash in some beef broth as needed or desired. Stir in green onion.
Serve over brown right, in lettuce cups, or on its own.