Heat oil in a sautee pan. Place onions in pan and season with salt and pepper. Cook onions until soft. Add shrimp, cook both sides until just turning pink. Add broccoli. Cover and cook for 5 mins until broccoli fork tender and bright green.
In a small bowl mix together soy sauce, sesame oil, pepper flakes and garlic. Pour over the stir fry and cook for 1 minute. Serve immediately.