Cut the tofu into 3/4-inch cubes and soak in hot salted water for 10-15 minutes. Drain gently.
Toast the Sichuan peppercorns in a dry wok 2-3 minutes until fragrant, cool, then grind to a coarse powder. Set aside.
Heat the oil in a wok over medium-high heat. Add the doubanjiang and stir-fry 1 minute until it darkens and the oil turns red. Add the ground pork and Shaoxing wine; cook 3-4 minutes until no longer pink.
Stir in the garlic, ginger, and scallion whites; cook 30 seconds. Add the chili flakes and stir 15 seconds.
Pour in the stock, soy sauce, and sugar. Bring to a boil, then reduce to a steady simmer. Taste and adjust salt.
Slide in the drained tofu cubes. Push and nudge gently with the back of a ladle (do not stir roughly). Simmer 3-4 minutes.
Stir the cornstarch slurry and drizzle in while swirling the pan, until the sauce turns glossy and clings to the tofu, about 30 seconds.
Off the heat, sprinkle about 1 teaspoon of the ground Sichuan pepper over the top and add the scallion greens. Serve immediately over hot steamed rice.