There is a place, close to Mostar and even Dubrovnik, where you can eat some food which you can't anywhere else.
Near Siroki Brijeg in west Hercegovina you can find a few restaurants where u can order a species which doesn't exist anywhere else except here. Small sweet-water fishes and crabs, together with local frogs, from the nearby river. Those fishes and crabs only can survive in very clean water, so the quality of the food is guaranteed.
If sometimes you are in the area, just contact me and I will give you direction guides and my recommendation to the host of the restaurant.
Enjoy your meal!