Korean fish cakes have a texture similar to firm tofu. If they're not to your liking, substitute with spicy Korean rice cakes (dduk bok ki) instead. You can also serve this soup with a peeled, hard-boiled egg if desired.Korean fish cakes have a texture similar to firm tofu. If they're not to your liking, substitute with spicy Korean rice cakes (dduk bok ki) instead. You can also serve this soup with a peeled, hard-boiled egg if desired.