These are actually deep fried fishcake fritters and are usually eaten as a snack/side. They are served with a sweet & sour sauce (mostly sweet) and cucumbers; when eaten on the go, these are cut into bite-sized pieces and placed in a box before being drenched in the sauce, and garnished with cucumbers to add some freshness. The fritters remain wonderfully chewy, and it doesn't taste as oily/greasy in that way.
These were from Jakarta, but if you're in Surabaya, one of the more famous ones are from Pempek Farina which I favour actually, because you can really taste the fish!