Step 1

Line a large plate or small, rimmed baking sheet with a tea towel.

Step 2

In a wok or large flat-bottomed skillet over high heat, heat the oil until it shimmers. Add the tofu in one layer — you may need to do this in batches — and fry, flipping occasionally, until lightly browned on all sides, about 8 minutes. Transfer to the prepared plate or baking sheet to drain.

Step 3

Pour off all but 1 tablespoon of the oil — reserving it for another use — and return the pan to high heat. Add the white parts of the spring onions or scallions and the zucchini, and stir-fry, stirring occasionally, until the vegetables take on color, about 4 minutes.

Step 4

Make the sauce: Meanwhile, in a small bowl or liquid measuring cup with a spout, stir together the cold water and cornstarch or potato starch. Stir in the garlic, ginger, soy sauce, rice vinegar, and the doubanjiang, chili-garlic sauce, oyster sauce or additional soy sauce.

Step 5

Add the sauce to the wok, and let it come to a boil and thicken, about 1 minute. Remove from the heat and stir in the tofu until well coated with the sauce. Garnish with the scallion greens and serve, with rice, if desired.