Smash the tofu in a large bowl. Combine cornstarch with water.
Heat 2 tablespoon of cooking oil (or you can use 1 tablespoon) and fry doubanjiang over slow fire for a while until the oil turns red. Add garlic and ginger, fry until aromatic.
Place tofu in, add sugar and light soy sauce. Let the tofu simmer for 4-5 minutes over slow fire.
Gently stir the starch water to avoid the starch settling to the bottom. Pour in the starch water in the tofu and make a quick stir to combine everything. Then place half of the scallions in. Combine well. Transfer out and sprinkle the remaining scallion as decoration.