Combine the first seven ingredients, stir well, and refrigerate for 4-24 hours.
Cut and discard the stems from the broccoli, and separate the florets (there should be about six cups). Steam in a small amount of heavily-salted water until tender-crisp and bright green, about three minutes. Drain and rinse under cold water to stop the cooking.
Heat the olive oil in a wok or large saucier over high heat. Drain the beef, reserving the marinade; add the drained beef to the pan and cook until no longer pink, about 4-5 minutes. Add the vegetables, cover the pan, and cook another 4-5 minutes; then uncover it and cook an additional five minutes, stirring the while and letting the liquid reduce.
Whisk the flour into the reserved marinade and pour it into the pan. Cook, stirring vigorously, until sauces boils and thickens.