Method:

1. Place all the marinade ingredients into a bowl with the beef. Toss through to evenly coat and allow to sit for 15 minutes (optimally 30 minutes if you have the time).
2. In the meantime, prepare vegetables.
3. Heat a large wok, and then add half the beef. Cook the beef for only 2 minutes. Remove and add the second batch. Cook for 2 minutes as well.
4. Add back into the pan the beef along with the onion, red capsicum, and a dollop of butter and continuously stir, cooking for a further 3 minutes.
5. In the meantime, place the corn flour in a quarter of a cup of ice water and mix to combine. Pour over the Beef along with a couple of tablespoons of the remaining marinade and bring to boil. Once boiling, remove from heat. Allow sitting for 2 minutes.
6. In the meantime, arrange the watercress or rocket on a platter and place the beef over the top along with a large handful of bean sprouts.
7. Serve and enjoy on its own or alongside steamed rice.