I love this dish. It's full of flavor, and takes minutes to cook. This is definitely, one of my favorite suppers. This is essentially 3 stir fried dishes in one - stir fried spinach, beef in oyster sauce and mushrooms in tangy vinegar.
This dish uses all my top store cupboard ingredients: groundnut oil for the stir-fry, light soy sauce, Shaohsing rice wine, Chinkiang black rice vinegar and dried chile flakes. It also has oyster sauce in it. Try and find an oyster sauce which doesn't have chemical additives or Monosodium Glutamate (MSG) in it - some people are allergic to MSG so check the label to make sure that it doesn't have flavor enhancers.
This is a balanced dish because of the use of spinach - (yin) and meat and garlic (yang). Stir frying has a neutral element. You can serve this with plain Jasmine rice or just with the spinach and mushrooms.
To make the beef: Prepare the fillet of beef by hammering it with a meat cleaver, the side of a meat cleaver, the side of a Chinese cleaver or a rolling pin. Slice it thinly, and put the pieces into a bowl. Season the beef with the light soy sauce, oyster sauce, salt, black pepper, and sugar. Set aside.
Heat a wok over high heat, and add 1 tablespoon groundnut oil. Add the garlic, and chile, and toss quickly. Then, add the spinach leaves, and toss so they warm for 5 seconds. Scatter them onto a large serving plate.
Heat the wok over high heat, and add the remaining groundnut oil. Add the beef slices, and stir-fry for 1 to 2 minutes, adding a dash of Shaohsing rice wine. Season with a pinch of dried chile flakes. To serve, lay the beef over a bed of the garlic-spinach leaves.
To make the mushrooms: Reheat the wok, add the oil, then add the oyster mushrooms and stir fry for 1 minute. Add a small splash of water to create some steam to help cook. Season with the black rice vinegar, and light soy sauce. Spoon the mixture over the beef, and serve.