Pick the flesh of the galunggong, carefully removing small bones, and shred coarsely.
Add 1/2 tsp. of salt to the shredded potatoes, mix then squeeze out the excess water. Squeezing out the water ensures crispiness of the fried fish cakes. If you do not squeeze out the water, the fish cakes will turn soggy within a few minutes after cooking.
Mix together all the ingredients except the cooking oil.
Heat the cooking oil to smoking point.
Form the mixture into patties. This can be tricky since the ingredients don't really stick together well. I suggest you form a patty with your hands, invert it onto a spatula then slide it carefully into the hot oil. Fry the patties in batches of three or four until golden. Flip over halfway through cooking to ensure uniform color and crispness. Drain on paper towels and serve with your favorite dipping sauce.