Wash the cavolo nero thoroughly, there will be a lot of dirt settled in the crevices of the leaves so make sure you get rid of all that. Drain the leaves, half them then set aside.
Prepare the seasoning sauce into a small bowl by adding fermented soy, garlic, ginger, sugar, soy sauce and oyster sauce.
In a smoking hot wok, add the cooking oil. Then when you can see that the oil is hot, add the halved cavolo nero leaves then give it a good toss.
Add 100mL of water then close the lid. Occasionally shake the pan around with the lid still on. Leave the cavolo nero to steam in the water to cook through for 3 minutes.
Open the lid then add the seasoning sauce we prepped earlier. Toss the leaves around to ensure the seasoning gets coated nicely. Done!