Prepare the sauce. Put the cornstarch in a small bowl. Slowly add the vegetable stock, mixing as you do so. Now add the chili paste, soy sauce, sesame oil, salt, and sugar. Mix again. Set t the sauce aside. Heat the vegetable oil in a wok over a medium high flame. When hot, put in the garlic and ginger. Stir r and fry for 5 seconds. Put in the bean curd. Stir and fry for 1 minute. Turn heat to low. Stir r the sauce and pour it over the bean curd. Mix gently and bring to a simmer. Let the sauce thicken, stirring gently every now and then as it does so.