1. In a small bowl, whisk together 2 tablespoons of water, the soy sauces, vinegar, sugar, 1 teaspoon of cornstarch, and salt until well combined.
2. Cut the tofu into 1-inch cubes and transfer to a large bowl. Rub with the remaining 3 tablespoons of cornstarch until all sides are lightly coated.
3. Pour enough oil to coat the bottom of a large non-stick pan and set it over medium heat. Add the tofu into the hot oil and panfry until golden brown all over, 1 to 3 minutes per side, adding more oil if the pan looks dry at any point. Transfer to a plate.
4. Using the same pan, sauté the ginger until fragrant, 2 to 3 minutes, adding more oil if the pan looks dry. Add the chiles, garlic, and white parts of the scallions. Stir-fry for about 1 minute, until the garlic is fragrant.
5. Add the tofu, sauce, and Sichuan peppercorns (if using), then quickly toss until the tofu is evenly coated with sauce, about 1 minute. Fold in the remaining green parts of the scallions and the peanuts.
6. Serve warm with a bowl of rice.