This was so good I'm never getting Chinese take away again;) I didn't use specific measurements.
Heat peanut oil in wok on high, then add beef and stir-fry until browned. Remove beef and set aside. Add sesame oil to wok, then add broccoli and garlic powder and stir-fry for 1-2 minutes, then add water and oyster sauce and bring to boil. Simmer until sauce thickens, then add in cooked beef and fish sauce. Mix well and serve over rice.