Cut bangus at the back, from head to tail.
Remove gills and entrails. Wash well.
In a bowl, combine onion, tomatoes, garlic and mashed alagaw leaves.
Let mixture stay for about 5 minutes.
Stuff the bangus with the marinated mixture.
Wrap in banana leaf and simmer in vinegar-soy sauce for 15 minutes.
Pat dry bangus in absorbent paper towel.
Deep-fry while still wrapped in banana leaf until fish is golden brown.
Unwrap and place on a serving platter. Pour the vinegar-soy sauce mixture.
lf desired, the fish can be served with the vinegar-soy sauce as individual dip. Serve hot.