Cut the pork belly into thin slices, about ⅛ inch thick, cutting so that each piece ends up with striations from layers of fat and meat.
Trim the leek, slice it lengthwise, then cut it diagonally into approximately 1½-inch-thick pieces. Separate the white and light green parts from the dark green parts.
Heat two tablespoons of oil in a wok or large frying pan over medium heat. Add the pork slices and salt. Cook for 6–8 minutes and stir-fry occasionally, until the fat renders and the edges turn crisp.
Push the pork to one side of the wok. Lower the heat to medium-low and add the doubanjiang. Stir-fry for about 30 seconds until fragrant and the oil turns red. Add the douchi and garlic and cook for another 30 seconds.
Add the white and light green parts of the leek. Increase the heat to medium and stir-fry for 1–2 minutes, until slightly wilted.
Add the green parts of the leek and the sugar. Stir well to combine, and cook everything for 1 more minute. Season with more salt to taste, if needed, and serve hot with lots of rice.
