Lay the chicken breast on a chopped board and, holding your knife at a right angle to the board, cut it into thin slices. Place in a bowl. Add the marinade ingredients with 2 teaspoons cold water and mix well.
Holding your knife at a steep angle, cut the spring onion on a bias into 3/8-inch (1 cm) slices, keeping the white and green parts separate. Clean the oyster mushrooms if necessary and tear or cut lengthwise into bite-sized pieces, discarding any hard bits at the base of their stalks.
Heat a seasoned wok over a high flame. Add 1 teaspoon of the oil or lard, swirl it around, then add the mushrooms and stir-fry for a couple of minutes until nearly cooked. Set aside.
Reheat the wok over a high flame, then add the remaining oil and swirl it around. Add the chicken and stir-fry to separate the slices. When the slices are separating but still pinking, add the ginger, garlic and spring onion whites and continue to stir for a few moments until you can smell their fragrances. Then return the mushrooms and stir to incorporate, adding salt and pepper to taste. Finally, stir in the spring onion greens, then serve.