Last saturday I went to Mochica (3863 St. Denis, 514-284-4448), a newly opened Peruvian restaurant that I had just noticed the day before. The restaurant is named for a pre-Inca peruvian civilization, and bills itself as peruvian gastronomy; it apparently uses many ingredients specially imported from Peru (for instance aji, a peruvian chile, and some odd-shaped corn that I'd not tasted before). The decor was quite beautifully done - sober and elegant like a trendy urban restaurant, but with understated peruvian touches (the pyramidal back supports of the chairs were very clever, I thought). The menu has a definite fish and seafood bent, although some meat dishes are offered (including llama !). For appetizers I had the fish ceviche, which was somewhat different from the central american ceviches that I've had before; the fish was not excessively marinated (and thus retained a lot more flavor and texture and was not too acidic), and it was served dry rather than in the usual slurry. It was served with a bit of an ear of the aforementioned corn (white, with large grains), corn puree, onions and yams. For the entree I had a seco de cordero, a stew of marinated lamb served with a coriander sauce; it was very tender, flavorful and delicate, if a tad overdone. It was served with excellent frijoles (light, with a fluid sauce - nothing like the usual goop), fine white rice and a peppered mesclun salad. For dessert I had the noche y dia cake, four layers of alternating chocolate and white cakes, lightly soaked in a sweet sauce of coconut and some other ingredient whose name I failed to grasp (one of many - the waitress was quite informative on the various ingredients used). All in all it was an excellent meal, and I would recommend this restaurant to anyone who wants to have a fine meal a bit off the beaten path. I have no experience of Peruvian food and can't comment on whether it was "authentic", but frankly who cares about authenticity if the food is good ? Prices were a tad on the steep side (appetizers 8-16$, entrees 20-36$), but that seems to be the trend for upper-mid range restaurants on the Plateau. The one deplorable thing about the restaurant was how empty it was (while all neighboring places were packed solid), with just one other table of diners while I was there. But this may just be because of its recent opening.
By your description of the ceviche it sounds like you got the real peruvian dish, (Peru and Ecuador claim to be the birthplace of ceviche and serve it with different garnishes), not the pickled fish that passes as ceviche in most other places. Whether it was absolutely authentic or not it would depend on the type of lemon used, the necessary small round and delicate "limones" are difficult, if not impossible to find where i live, western canada.