In a bowl, combine the pork liver and ½ cup vinegar. Let it marinate for 30 minutes. This will help tenderize the liver and give it a nice tangy flavor.

Heat 1 tbsp cooking oil in a pan over medium heat. Add the ground pork lungs and sauté until it's browned and cooked through. Remove from the pan and set aside.

In the same pan, add the remaining 2 tbsp cooking oil. Sauté the garlic until fragrant, then add the onion and cook until translucent.

Add the pork kasim cubes into the pan. Cook until the pork is lightly browned and its natural fat starts to render. This should take around 5-7 minutes.

Add the bay leaves and dried oregano. Stir well to coat the pork with the spices. Then, add the cooked pork lungs back into the pan.

Pour in ¼ cup vinegar (adjust based on your taste preference). Let it simmer without stirring for a few minutes to cook off the strong vinegar taste.

Drain the pork liver from the vinegar marinade and add it to the pan. Mix everything well and cook for another 10-15 minutes, stirring occasionally, until the pork liver is cooked through but still tender.

Season with salt and pepper to taste. Adjust the vinegar if needed, depending on how tangy you like it.

Once everything is well-cooked, turn off the heat and serve your Kapampangan Pork Kilayin with hot rice!