Cut tofu into 1-inch pieces and transfer to a large ziploc bag. Add soy sauce and maple syrup. Gently flip the bag a few times to coat tofu with the liquid. Marinate for 10 to 15 minutes.
Mix all the sauce ingredients with 2 tablespoons water in a small bowl.
When tofu is marinated, open the bag just a little bit without letting the tofu fall out. Drain the liquid and discard it. Add cornstarch, a tablespoon at a time, and gently toss the bag to coat the tofu. It is OK if the tofu isn’t coated evenly.
Heat a large skillet with 2 tablespoons oil over medium heat until hot. Add the tofu with your hand (or a pair of tongs), shaking off any extra cornstarch. Let cook without moving for 1 to 2 minutes, or until the bottom turns golden. Flip to brown the other side. If the pan gets too hot, turn to medium or medium low heat. Transfer cooked tofu to a plate. Set aside.
Add the remaining 1 tablespoon oil and the Sichuan peppercorns. Cook and stir until the peppercorns turn dark (but not black). Remove the Sichuan peppercorns and discard them.
Add the chili pepper, garlic, ginger, and doubanjiang. Stir for 20 to 30 seconds to release the fragrance.
Add the bell pepper and green onion. Stir for 20 seconds.
Stir the sauce again to dissolve the cornstarch completely. Pour into the pan. Stir a few times until the sauce thickens.
Add back the cooked tofu. Gently toss to coat with sauce. Add the peanuts and give it a quick stir. Immediately transfer everything to a big plate.
Serve hot as main with steamed rice.
Notes
If you do not use doubanjiang, taste the tofu at the end and add a pinch of salt, if needed.