Cut Chinese scallion into 3-4cm sections. Chop garlic and slice ginger. Then cut the green onion into smaller sections too.
Place scallion section in wok and sautéed for 1 or 2 minutes until slightly seared.
Cut pork butt into thin slices and then marinate with starch, water, oyster sauce, dark soy sauce and pepper. Mix well until all the liquid is absorbed by the slices. Then add 1/2 tablespoon of sesame oil. Set aside for 10 minutes.
Heat wok firstly and then place oil in. Heat until the oil becomes warm but not very hot. Spread the pork slices in and let the stay for seconds. Wait until the surface changes color. Move the pork slices to the edges of the wok (almost without fire). You can move your wok to make sure the pork slices are not continued to be cooked.
Place garlic, ginger and fermented black beans in. Fry for a while until aromatic. Place the long scallion section in. Add green onion in and mix well. Serve hot.