Mince the ground pork and ginger together. Remove the skin from the salted fish and mince it up with the pork and ginger until very well-combined.
Cut tofu into 2-inch squares about 3/4-inch thick. Scoop out about 1 teaspoon of tofu from each piece to make room for the meat. In a bowl, stir the excess tofu in with the pork. Add the wine, a pinch of fresh ground white pepper, and salt to the meat mixture. Mix well.
Divide the meat among the tofu pieces. Steam the plate of tofu in a wok or steamer for about 10 minutes.
While the tofu is steaming, mix 1 tbsp of cornstarch with 1 tbsp of water and set aside. Cut 4 to 6 pieces of the scallion about 3 inches long, and cut lengthwise slits on both ends. Put into a bowl of ice water. The ends curl up nicely and can be used as a garnish. Dice the rest of the scallions and set aside.
When the tofu is done, carefully remove the plate. Pour any excess liquid back into the wok and add more water if needed to make about a quarter cup of sauce.
Heat the liquid to a simmer and add the oyster sauce and dark soy. Season with a bit of salt and white pepper, and add the cornstarch slurry. Simmer the sauce until it's thick enough to coat the back of a spoon. Pour the sauce over the tofu and garnish with scallions.