In a bowl, whisk together the 4 tablespoons of soy sauce, brown sugar, mirin, garlic, ginger and onion powder cornstarch, water, sugar, sesame oil, garlic, ginger, onion powder. Set Aside.
Place the beef strips in a bowl and add ½ teaspoon of baking soda, toss to coat and leave to sit for 12-15 mins.
Heat a wok or large frying pan over a medium high heat.
Add the beef strips once wok is hot and fry till lightly golden. (this is important as you want to sear the beef (do not use a frying pan or wok that is too small, the beef should not overcrowd the pan).
Remove and set aside.
Add the sauce to the wok and heat until it reduces down and thickens a little.
Add the beef strips back into the wok with the sauce and fry for a further 2 mins just to coat the beef in the sauce.
Sprinkle with finely sliced spring onions and a pinch of sesame seeds.
Serve with your choice of sides.
