Heat the Sichuan peppercorns in a dry small frying pan over medium-high until just starting to smoke, tossing or stirring occasionally, about 3 minutes. Transfer the peppercorns immediately to a mortar and let cool, then use the mortar and pestle to grind to a fine powder. Set aside for later.

Heat a medium saucepan of water over high. Meanwhile, drain tofu and cut into bite-sized cubes. When the water is at a gentle simmer (a rapid boil would make the tofu crumble), add a generous pinch of salt. Carefully add the tofu pieces. Simmer gently for 2 to 3 minutes, then turn the heat off and allow the tofu to steep.

To a wok or large frying pan over high heat, add the vegetable oil. When the oil is hot, add the ground pork and cook, breaking up the meat, for 2 to 3 minutes, until the pork is no longer pink. Add the doubanjiang and cook, stirring, for about 2 minutes. Stir in the garlic, ginger and chile powder. Stir-fry for 30 seconds. Add the chicken stock, soy sauce, sugar and vinegar. Bring to a simmer then turn the heat down to medium and cook, until the liquid has reduced by about one-fourth and is starting to thicken, 3 to 4 minutes. Stir in the cornstarch slurry and the ground Sichuan peppercorns and let simmer until thickened, 1 to 2 minutes.

Use a slotted spoon to drain the tofu and gently stir it into the pork mixture. Simmer until slightly thickened, 1 to 2 minutes more. Taste and season with salt or soy sauce if needed. Remove from heat, drizzle with the sesame oil and gently toss. Transfer to a serving bowl and sprinkle with scallions. Serve with steamed rice.