In medium bowl combine soy sauce, water, mirin, Worcestershire sauce, ginger and cornstarch.
Heat olive oil in large skillet over medium heat. Cook onion for 1-2 minutes. Add beef and cook until browned; approximately 4-5 minutes. Add garlic and cook for 1 minute. Add soy sauce mixture and cook for 2 minutes. Add broccoli and cook until crisp tender and sauce is slightly thickened; approximately 5 minutes. Serve over rice or Chinese noodles.
You need a pretty good cut of beef. I use either petite shoulder, tenderloin, sirloin, tri-tip, ribeye or strip.