Our favorite restaurant in Ljubljana turned out to be the one recommended by the owner of the apartment we were renting. Slovenska Hisa Figovec was only a 5 minute walk away and featured traditional Slovenian food, which is exactly what we wanted to try. We enjoyed their food and service so much we returned for a second dinner during our 3 day stay.
The restaurant is centrally located in a historic inn more than 200 years old, although the restaurant only opened in 2017. The interior is warm and cozy and it is busy, so it's not a bad idea to make a reservation. During our second visit several large tables in restaurant were occupied by tour groups (Rick Steves), so having had our own reservation ensured we could get a table. ,
Slovenian food traditionally was mostly cooked for hard-working people. It is hearty, filling food (although not that greasy), and portions were enormous. It was difficult to eat everything on our plates. I had my camera at only one meal, but I think these photos give you a good idea of what the food is like.
We started the meal with "Struklji", a savory cottage cheese roll roasted with butter and served with a sauce of creamy wild garlic. The sauce was to die for! I enjoyed the dock worker's meal (Leteci zganci) -- fried chicken with pan-fried potatoes and onions --amazingly good. My wife had the pork schnitzel (Ljubljanski zrezek), which she also enjoyed.
For dessert we shared a piece of a traditional layered Slovenian cake known as Prekmurska Gibanica. Good and especially recommended for those who don't like their desserts too sweet (my favorite cakes remain Black Forest, or some combination of raspberries and chocolate).
The restaurant features vegetarian options if that's what interests you, and it has an excellent local wine list. I'm more of a beer guy when eating traditional or peasant food.
The prices were very reasonable and you won't leave hungry. A recommended spot if you want authentically prepared and traditional Slovenian food.