Toss the beef to coat in the sauce and leave at room temperature to marinate for 30 mins. When you are ready to cook cut the broccoli up into bite sized florets.
Heat a wok or high sided fry pan over high heat with a tablespoon of cooking oil. When the pan is hot add the marinated beef and stir fry for a few minutes until the beef has developed some colour.
Remove the beef and place into a clean bowl. Turn the heat down and add a small amount more oil to the wok if necessary and pour in the broccoli florets.