Mash 2 bananas in a bowl, leaving some texture if desired.

Mix glutinous rice flour, salt, and mashed bananas to form a dough.

Shape the dough into small portions and flatten them on your palm.

Place banana slices or mashed banana in the center of each portion and shape into desired forms.

Grate castella cake into fine crumbs for coating.

Boil water in a pot and cook the rice cakes until they float to the surface.

Transfer the cooked rice cakes to ice water to enhance chewiness.