Remove the beef from the fridge an hour before you would like to start cooking to bring it room temperature.
Heat a large frying pan or wok until hot (no need to add any oil).
Add the marinated beef strips to the hot pan and allow to sizzle over a medium heat for around 5 minutes, until cooked to your liking. Remove the pan from the heat and cover with a lid and leave to rest while you prepare the other ingredients.
Bring a large pan of water to the boil, add a little salt then add the broccoli florets and blanch until the stalks start to become tender, then add the courgette ribbons and allow to soften for just 1-2 minutes. Drain the water from the pan then add the blanched vegetables to the frying pan with the beef. Replace the lid.
Lastly, toast the sesame seeds in a pan over a medium to high heat, tossing the sesame seeds frequently for just a few minutes until you hear the first pop of the seeds and remove from the heat to ensure they do not burn.. The difference from toasted to burning is only a few seconds!
Place the frying pan with the beef and vegetables over the heat for just a minute or 2 to ensure the food is hot and ready for serving. Serve with a scattering of the toasted sesame seeds and season to taste.