Prepare the sauce: In a small bowl, mix soy sauce, calamansi or lemon juice, liquid seasoning, brown sugar, water, cornstarch, and pepper. Stir until the sugar and cornstarch are fully dissolved, then set aside.
Prepare the bangus: Season with salt and pepper, then coat evenly with cornstarch or flour to help it crisp up when fried.
Fry the bangus: In a frying pan over medium-high heat, add about ¼ inch of cooking oil. Fry the boneless fillets until crispy and golden brown. Remove from oil, drain on paper towels, and transfer to a platter or sizzling plate.
Sauté the aromatics: In a small skillet, heat extra virgin olive oil (or butter) over medium heat. Sauté garlic until golden, then add shallots (or onion rings) and cook until lightly browned.
Add the sauce: Pour in the prepared sauce and stir as it cooks. Let it thicken, then turn off the heat. Give it a taste and adjust as needed.
Dress the fish: Spoon the warm sauce over the fried fish. Top with scallions, crispy shallots or garlic bits, and chilies, if desired.