Marinate the Beef:

In a bowl, mix the beef slices with soy sauce, cornstarch, and sesame oil. Let it marinate for at least 15 minutes.

Prepare the Bitter Melon:

Slice the bitter melon in half lengthwise, scoop out the seeds and white pith with a spoon, and slice thinly.

Stir-Fry the Beef:

Heat 1 tablespoon of vegetable oil in a wok or skillet over high heat. Add the marinated beef and stir-fry until it's no longer pink. Remove the beef and set it aside.

Cook the Bitter Melon:

In the same wok, add the remaining oil. Sauté the garlic until fragrant, then add the bitter melon slices. Stir-fry for 2-3 minutes.

Combine Ingredients:

Add the fermented black beans, oyster sauce, and soy sauce to the wok. Return the beef to the wok, add water or beef broth, and mix well. Cook for an additional 2-3 minutes, allowing the flavors to meld.

Season:

Taste and adjust the seasoning with a pinch of salt and sugar if necessary.

Serve:

Serve hot with steamed rice.