To prepare the gravy, heat the oil and add the scallions to it. Add the ginger and garlic after about a minute and a half, and continue to fry. Remove all of it in less than 2 minutes, and set aside. In a bowl, mix the cornflour, soy sauce, salt, and a cup of water without letting any lumps to form. Add in the ketchup and the remaining ginger-garlic paste to a pan and fry. Add the cornflour mixture to the pan and simmer till thick. Your sticky gravy is ready. Mix the cauliflower fritters, gravy, and fried onion mixture together, and serve.