Cut tofu into 1-inch thick slices and pat dry. Heat a generous amount of oil in a shallow frying pan. Once the oil is hot, add tofu and fry until both sides are golden, flip once. It may take 3-4 minutes each side. Transfer to a wired rack or a plate lined with paper towel to absorb excess oil. Don't wash the pan yet.
While frying the tofu, place ground pork in a mixing bowl. Add the minced garlic, white part of scallion, salt and pepper in the "For the Stuffed Tofu" section to the bowl. Mix to combine, then set aside.
Let the tofu cool down enough to handle. Use a paring knife to make a horizontal slit in the middle but do not cut all the way through. Add the ground pork filling to the tofu pocket.
Discard most of the oil in the pan, leaving enough to coat the bottom generously. Place over medium heat to heat the oil, and then add the stuffed tofu meat side down. Sear for a couple of minutes until the meat side is browned. Remove the tofu and set aside.
Wipe the pan clean, and then add a small amount of oil to coat the bottom. Heat over medium heat and when the oil is hot, add minced ginger. Sauté for about a minute until fragrant.
Add minced garlic and white part of scallions to the pan and continue to sauté briefly until fragrant. Then add fermented black beans and cook for another 1-2 minutes.
Add oyster sauce and soy sauce and stir well. Then add ¾ cup water and bring the sauce to a rapid simmer. Dissolve cornstarch in the remaining 1½ teaspoons water and slowly pour it into the pan while stirring.
Add stuffed tofu to the black bean sauce and simmer gently for 3-4 minutes to soak up the flavors, flip once. The sauce will also thicken. Adjust the seasonings and thickness to your liking. Stir in the toasted sesame oil if using.
Transfer stuffed tofu along with the sauce to serving plates. Sprinkle with green part of scallions. Serve right away with steamed rice.