Heat a wok or large skillet over the highest heat. Pour in two tablespoons of the oil, and when it is shimmering, add the tofu and stir-fry until golden brown, about four minutes. Transfer the tofu to a plate with a slotted spoon.

In the same pan, heat the remaining four tablespoons oil and, when the oil is shimmering, add the green beans. Cook, stirring occasionally, until the green beans are somewhat shriveled and developing black spots in many places. Depending on the heat of your stove, this may take anywhere from four to 10 minutes. Add the mushrooms and stir-fry for one minute more. Turn off the heat and drain the green beans and mushrooms in a colander, leaving about one tablespoon oil in the pan.

Return the pan to the heat. Cook the Sichuan preserved vegetables, ginger, and garlic for 30 seconds, until very fragrant. Return the green beans, mushrooms, and tofu to the pan and toss to combine.

Whisk together the soy sauce, sesame oil, sugar, and salt, and pour over the green beans. Toss to coat, cook for 30 seconds more, and serve immediately.