In researching agriturismo restaurants in north-central Istria, everyone said the same thing: "You must go to Tončić." Nestled in the hills near Oprtalj, this restaurant was so good that we went twice, in one day.
This is simple food, extremely carefully and capably prepared. Orjeta and Sandro Tončić prepare what's freshest—there's no menu, and just a few choices each day. They make everything themselves, or source it locally—from the cheese and pršut (prosciutto) on our affettati misto plate to the rolled pasta called fuži, topped with young porcini mushrooms and gnocchi with a wild boar sauce. That was lunch (plus the local malvasia wine and a few glasses of grappa). We came back for dinner and had a salad of radicchio, beans, tomatoes, and carrots. The grilled lamb chops that had been marinated in oil for seven days were extremely tender.
Agroturizam Tončić is at Čabarnica 42, just outside Zrenj. There are signs for it around town. It's open for lunch and dinner Thursday–Sunday. I wish I could go back right now!