I often come to Valvasor for lunch. The lunch menu (choice of fish or meat) is incredible and great value for the money (10 - 11 euros). Compared to a la carte, lunch menus are much tastier and more innovative. Although I think Valvasor is one of Ljubljana's top 3 restaurants, I can say that a la carte is overpriced.
The only downside to fish lunch menus is that if you're late, sometimes you'll find they have run out of fish and they'll offer you the same meal with another sort of fish which is not as good or doesn't go equally well with the rest of the meal. So if you don't like the replacement fish, you have to choose the meat menu.
Both fish and meat menus are excellent, but I find fish menus better overall.
Top notch service. Waiters are polite and mostly unobtrusive, as you'd expect in such a chic restaurant. Atmosphere is posh, but not in an intimidating way. The indoors is very well lit and there are always fresh flowers.
Valvasor is frequented by many businesspeople and foreigners (those who live in Ljubljana or have come to the city for meetings, not only tourists), which makes it a lovely small cosmopolitan enclave in the heart of the Old Town.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.