1. Prepare the sauce: Rinse the black beans to remove any grit. In a small bowl, mash the black beans with the back of a spoon. Combine the black beans with the chicken stock, chili bean paste, rice wine, soy sauce, sesame oil, sugar, and Sichuan pepper. Set aside.

2. Heat a wok or large pan or wok over high heat. Add the cooking oil and swirl to coat the base. Add the pork and stir-fry until crispy and starting to brown but not yet dry, about 2 minutes, breaking up the pork with a spatula. Reduce the heat to medium, then add leeks, garlic, and ginger and stir-fry until fragrant, about 1 minute.

3. Pour in the sauce and bring the liquid to a boil, the reduce to a simmer. The liquid should now have a nice red color. Gently add the tofu cubes, being careful to not move them around too much or else they will break up. Allow the sauce to simmer for about 2 to 3 minutes so the tofu can cook and absorb the the sauce.

4. Carefully push the tofu to the sides and create a small well in the middle. Stir in the cornflour mixture in the center. Allow the liquid to simmer for another minute, until the sauce has thickened enough to coat the back of a spoon. Transfer to a deep plate or wide bowl, sprinkle spring onion on top, and serve hot with steamed rice.