In a casserole start by warming up the oil. Put the garlic and onion. Sauté them until they become translucide. Add the pounded chicken liver and continue mixing. Put some salt and pepper . Pour the pork broth and let it simmer gently for about thirty minutes. Add the soy sauce and sugar. Continue mixing. Pour the vinegar and taste if it needs more sugar or salt. Then get a laddle of this broth and dissolve the cornstarch before adding it up in your sauce or sarsa. Mix well to avoid having lumpy part. Taste and turn off the fire. It the sauce is too runny add more cornstarch but be sure to dissolve it first on some liquid before adding. The sauce will thicken more if it stays longer on the stove. You can also replace the pork broth with chicken broth; This sauce is an all around sauce you can use for lechon, fried pork or chicken or even fried fishes.