Prepare the bangus fillet by slicing the back of the bangus an spreading it like a butterfly. Just like when you are making daing na bangus. (If you can buy boneless bangus or boneless bangus belly, it will save you time.)
Then remove the skin and backbone. Then debone the bangus fillet. Chill for 1 to 2 hours and cut it into chunks. Lightly salt the chicken livers also before cooking.
Heat up a non-stick stove top grill and brush with 1 tablespoon cooking oil. Grill the bangus chunks on all sides until the meat turn white and sides are brown. Transfer to a plate with paper towels to absorb excess oil. Set aside.
Grill the chicken livers until brown and cooked. Then chop it finely and set aside.
In a bowl, combine grilled chicken liver, bangus chunks, onions, green chili peppers, calamansi juice, ground pepper and salt. Toss and mix the ingredients well.
Heat a sizzling plate on a stove and put the margarine until melted and sizzling. Then place the bangus sisig mixture in the sizzling plate and toss lightly until the margarine coats all the ingredients and the onions are slightly soft and fragrant.
Turn off heat and transfer the sizzling plate with the bangus sisig on a wooden tray and serve hot.