In a pot, heat a tablespoon of cooking oil in medium heat and saute the garlic until fragrant. Then add the onion and saute until soft. You can also season the onion and garlic with pepper but this is optional.
Then pour the patis and let it simmer for half a minute then put the pork in the pot. Increase the heat and start stirring the pork.
Stir fry until the pork is brown and render some of the fat. Remove the fat from the pot and leave just a small amount for the dish.
Then pour the vinegar in the pot and let it simmer for 2 minutes without stirring. Next is pour the water in the pot and bring to a boil.
Let it simmer until the pork is tender. Add in the pepper and finger chilies. Simmer again for 2 minutes. Adjust the taste if necessary.
Then pour the pork blood and bring to a boil without the lid. Add the sugar if the broth is too sour.
Sugar is for balancing the taste of the vinegar. Cook for another 3 minutes or until the blood is cooked as per your preference. Serve hot with rice or puto.