Make just enough of this recipe. Use the portion planning tool to calculate exactly how much of each ingredient you’ll need.Cut the beef lengthwise (with the grain to start) into strips 5-8 cm wide. Then cut the strips across the grain into very thin slices. (Tip: Easier if the meat is partially frozen)Toss the meat in the soy sauce and sprinkle cornstarch over the meat. Marinate for 30 minutes.Slice the button mushrooms, and cut the broccoli tops and set aside.Slice the garlic and ginger and set aside.Place a wok or large fry pan on medium to high heat, add the oil.Add the beef and cook until the meat starts to turn brown – about 2 minutes. Cook only half way, then remove and set aside.Add the garlic and ginger and cook for 1 minute. Add the broccoli and mushroom.When the vegetables are half cooked add the meat back in and stir.Add the black bean paste and mix well. If stock is needed add it at this time. Do not let the sauce reduce or the meat will overcook. (you can use your choice of sauce)Serve at once.