Step 1Add 2 inches of water to a medium pot and bring to a boil. Add the tofu sticks, breaking them if necessary to submerge them. Remove from the heat. Weight down the sticks with a plate that fits inside the pot. Cover and let sit for 30 minutes.
Step 2Remove the plate and drain the tofu well. Cut the sticks into 2-inch lengths, trimming and discarding any tough bits. Cut the sticks lengthwise in halves or into quarters, to make narrow batons. Set aside.
Step 3Heat a wok or wide heavy pot over medium-high heat. Add the peanut and sesame oils. When the oil is hot, add the chile pepper flakes and the tofu batons and stir-fry for 2 minutes, stirring and pressing on the batons to expose them to the hot surface of the pan.
Step 4In a small bowl, combine the vinegar, soy sauce and sugar and whisk well, then pour over the tofu batons. Stir-fry briefly to distribute the flavors, and continue to cook until the liquid is mostly absorbed. Remove from the heat.
Step 5Turn out into a wide shallow bowl. Sprinkle with the cilantro and serve warm or at room temperature.