There are 2 methods for black bean sauce:
The first is a cheat method where you buy the sauce in a jar/can from a Chinese supermarket like Wing Yip. You can even find this in mainstream supermarkets these days although they usually stock duff brands.
Heat up the wok with a little peanut oil.
Heat up the sauce.
Add chopped Beef (why not treat yourself to some fillet beef)
Done
The second method is to prepare the sauce from scratch.
Prepare the beef by slicing into strips and then soaking in a tablespoon of Soy sauce (I recommend Kikoman C00039)
Heat up the wok with a little peanut oil.
Add the following to the oil:
2 teaspoons of sesame oil
2 tablespoons of chopped black beans
2 chopped cloves of garlic
1 tablespoon of ginger
Fry for about a minute and then add the following:
1 teaspoon of salt
1 chopped spring onion
2 teaspoons of soy sauce (I recommend Kikoman C00036)
150ml water
The marinated beef
Add 1 teaspoon cornflour mixed with 1 teaspoon water slowly until the sauce thickens
If you prefer it a little sweeter then add sugar to taste.