About an hour before you want to start cooking, slice the tofu into slabs—I usually make 5 uniform slabs. Put them in a glass or nonreactive baking dish in a single layer and marinate in 1/2 cup soy and the vinegar, turning after 20 minutes or so. Then drain on paper towels or a lint free cloth for a few minutes. Slice crosswise into strips about 1/2-inch wide.
Cut the bell peppers and the celery into strips too. It is nice to make them all the same size, but if like me you are having a tough day and just want your dinner, then don’t worry about it.
The next part happens pretty fast. Heat the oil in a seasoned wok or a heavy-bottomed nonstick skillet over medium. Then when it is well heated, add the peppercorns and the crispy chili sauce and stir fry quickly until it becomes all fragrant. Add the garlic and ginger and stir fry for another 30 to 45 seconds. Add the onion, peppers and celery, turn up the heat to high, and stir fry until thoroughly hot—about 60 to 90 seconds.
Sprinkle the sugar over everything, then add the 1/2 cup soy sauce and, if you were using Szechwan peppercorns, add a good grinding of black pepper. Put in the tofu now and carefully continue to stir fry until everything is wonderfully fragrant. Add the sesame oil and the scallions, stir, and you are ready to serve.
We served this with leftover linguine which we stir fried to lightly brown it, in a separate pan, in the manner of lo mein, but you can serve this with white rice or brown rice or just on its own.