My first tip for you is to slice the beef into 5 mm thick. Personally, I think this is the perfect thickness. I don’t recommend slicing it thinner than this because it will dry out quickly during the frying.
Normally I will season it with some Chinese cooking wine. But I am in Cuenca Ecuador now. I couldn’t find Chinese cooking wine in this whole city so I found out that same amount of beer works just fine. I thought this will be a good substitution for Chinese cooking wine. Do not use the dark beer. It will turn out a bit of bitter at the end. After that, I will add some salt and black pepper. If you get a cheap cut which might be tough, you can add 1/4 tsp of baking soda. It will help tenderize the beef. But if you get a nice cut, it is not necessary.
Let the beef sit for 30 minutes. We will coat the beef with some cornstarch. Give it a little mix to make sure the cornstarch is distributed so it won’t clump up later. Then we will add 1 and a half of egg white. Mix it again. After you make sure that every piece is coated nicely, you still want to keep massaging it for another 5 minutes to give it enough time to tenderize the meat. So this is my second tips. Cornstarch and egg white is a very common technique in Chinese cuisine. It gives a lot of moisture to the beef and creates a starchy layer to lock the juiciness inside the meat. So the beef will turn out super tender and juicy. Try it and you will be surprised.
Heat up 2 cups of frying oil to 370 degrees Fahrenheit. The most important thing is to get the oil to the high temperature so the beef will have a nice outside layer.
I usually put the beef as close as possible to the oil and then drop it in. In this way, the oil won’t splash everywhere. Add your beef piece by piece otherwise, they will clump up together. Make sure you fry them in batches because it overflows easily.
The oil is very hot so it will just take 1 or 2 minutes. Don’t fry it too long because you don’t want to overcook your beef. What we are looking for is the slightly golden color on the edge of the beef. I use a sieve to get rid of the excess oil.
Before we start the stir-frying process, let’s quickly make the sauce(2 tsp of cornstarch, 1 tbsp of oyster sauce, 3 tbsp of soy sauce, 3 tbsp of brown sugar, 2/3 cup of water, 1 tsp of dark soy sauce). Set the sauce aside, we will use it soon.
Heat up the pan. Add about 1.5 tbsp of cooking oil, 1 tbsp of minced ginger, 1.5 tbsp of minced garlic, and some white part of the spring onion. I like to use the white part for stir-frying because they don’t get soggy and I also reserved the green part to add at the end. Stir this until fragrant. Pour in the sauce. Stir it until it thickens up. Add the beef back into the pan. Mix everything together. Once you see the beef is coated with that shiny, thick, flavorful sauce, you can add some spring onion. Give it a final stir then take it out and serve it with white rice.