Add the thinly sliced beef strips into a bowl filled 1/3rd the way with water that's been mixed with the dark soy sauce and cornflour. Marinate in the fridge for at least 20 mins.

Heat a wok over a high heat and add in the oil. Once nice and hot add the onions and begin to fry. Move them around the wok so they don't catch.
Add in the beef (drain off all the water first), plus the chillies. Fry and brown off the meat on all sides.

Add the hoisin sauce and season with white pepper. Stir everything together then add the Mange-Tout. Toss all the ingredients together until evenly distributed. Serve up and enjoy. :)