Place the liver into a bowl. Add soysauce, liquid seasoning and calamansi juice. Add salt and pepper to taste. Place the bowl in the fridge and marinate for at least 1 hour.
On a hot skillet, add oil and butter. Fry the liver for about 3-4 minutes. Turn it over then fry again for about 4 minutes. Place on a plate and set aside.
On the same skillet, fry the potato chips until cooked. The drippings from the liver will give flavor to the potatoes. Sprinkle some salt and pepper. When cooked, put it on top of the liver.
Still on the the same skillet, add the left-over liver marinate. Turn off the stove. Add the onions. The heat will be enough to cook the onions. Then put the sauce and onion on top of the liver.