What kind of potato did you use to make it authentic Croatian?

Interesting. The recipe author didn't specify what type of potato was used (in Croatia) or should be used (outside of it) to make this dish. Seems like she wash showing us how the dish is constructed.
Seems like you want to go one step beyond that, or back to the recipe orgiins as much as possible.
If so, I suggest you look up what kind of potatoes are grown or commonly used in Croatia for food.
Doing that, I see at least one (russet) that is commonly used in USA.