Place the rump steak in the freezer for thirty minutes, this firms up the beef making it easier to slice thinly.
On a secure board slice the beef with a sharp kitchen knife into thin strips and place into a glass bowl. Add the marinade ingredients, mix well to combine together and fully cover the steak strips.
Cover and chill in the fridge for a minimum of two hours. Meanwhile, prepare the black beans by first rinsing thoroughly in cold water then soaking in fresh water for around half an hour, changing the water once. Drain thoroughly, chop finely and set aside.
When ready to cook, drain the meat from the marinade pouring any remaining marinade into a small, heavy-bottomed pan. Add the sauce ingredients to the marinade and heat gently to thicken, stirring occasionally to prevent lumps forming.
Heat the oil in the wok until smoking and carefully add the meat. Stir-fry until cooked, remove with a slotted spoon and set aside on to some kitchen paper.
Heat a little more oil then stir fry onion over medium heat for five minutes before adding the carrots and peppers, continue cooking for a couple more minutes until they are just starting to go soft.
Add the black beans and cook for two more minutes stirring continuously, be careful not to burn, then add the garlic, ginger, and chilli and cook for a further two minutes. Return the beef to the wok, strain the sauce through a fine sieve and add as well.
Mix in the sesame oil and cook for one more minute stirring all the time to heat the beef through and serve immediately with egg fried rice or noodles.