Happily, we did come across a restaurant that was still open post-opera (and not swamped with people like the cafes in Theater Square), Romeo's Bar and Kitchen:
We hadn't heard of it, but hunger drove away any No Baedeker (or Michelin) fears.
Fortunately, it was delicious. Per tradition whenever I am within a few countries of Germany, I got my schnitzel:
(Meat and potatoes. Quelle surprise)
Not pictured: Mom's outstanding beef stroganoff, which she ordered because we passed by the Stroganoff palace earlier on Nevsky Prospect in St. Petersburg. Apparently Count Stroganoff invented the dish because his bad teeth required him to eat only soft foods and small pieces of meat. It was one of the best dishes of our trip!