Chop the red onions and set aside.
Deboning a Bangus - If you were not able to get a deboned Bangus from the market (like me), you can actually debone it yourself. First, put enough water in a pan and add a little salt. When it boils, put the fish inside and cook slightly, just so it would be easy for you to flake it later. (Please do not overcook especially if you want to have your Sisig soft and tender afterward.) Drain the fish and flake it with your clean hands. Remove the bones and dice.
In a pan, combine the onions, vinegar, and peppercorns. Simmer this until the vinegar is reduced to 1/3 of its original volume and the onions are cooked and have turned into bright pink color. Set aside.
In a bowl, combine the soy sauce, oyster sauce, sugar, chili powder, salt, and pepper. In this mixture, marinate the Bangus for at least 30 minutes.
Heat oil in a pan and saute the garlic. Add the (pickled) onions, the marinated Bangus, and the marinade. Simmer.
While simmering, heat the sizzling plate on the stove. Brush it with a little oil. When the plate is already hot and the liquid in the Bangus is already reduced, transfer the Bangus mixture on the plate and spread it all over. Add whole egg and add a pinch of iodized salt on top of the egg yolk. Remove from heat and serve immediately. Mix it well upon serving to cook the egg and mix with the bangus sisig.
You may want to add a wedge of lemon for presentation or if you prefer it to be more sour.
Some also like to add a little bit of mayonnaise. Do if you prefer. Kainan na!
