Heat 1 T. oil over medium high heat.
Add broccoli and onions.
Stir fry for 7-10 minutes or until crisp tender. You may need to add some water to the pan if it gets dry and you need some moisture to keep the broccoli from burning.
While vegetables are cooking, in a separate measuring cup, mix together garlic, tamari, water, and thickening agent.
Scoot over vegetables, add additional T. oil to pan, and stir fry the beef for about a minute. You don't want it to get tough.
Mix together beef and vegetables after a minute and stir fry together for another minute.
Add sauce mixture to the stir fry and cook for about 2 minutes until beef is cooked through and sauce is slightly thickened.