Where to find traditional Brasilian/Paranese food
The official national dish of Brasil is feijoada, a stew of pork, black beans and many spices. Ask around with the locals to hear what their favorite feijoada restaurant is, most will serve it only on Saturdays. See also my Restaurant Tips for "Villa das Artes," a restaurant that serves a feijoada buffet on Saturday.
In addition to the national dish of feijoada, if you are in Curitiba, many will recommend that you try the official dish of the state of Parana (the state in which Curitiba is located.) That dish is called "barreado"--a beef stew that is simmered in a sealed clay pot for over 24 hours. Most people you talk to will tell you that the best barreado is to be had in the town of Morretes, just a train ride or an hour's drive away. I suggest taking the scenic train ride (Serra Verde Express) which will take you directly to Morretes, where you will have several barreado restaurants to choose from. See my Morretes page for detailed information about how to eat barreado, and for tips on at least two barreado restaurants there.
Finally, some say the official "drink" of Brasil is the caipirinha, made from a liquor distilled from sugar cane. It is mixed with sugar and lime (kind of like a mojito, but a different taste.) Refreshing, and yes, delicious. You can purchase little vessels with a pestle in souvenir shops, some have the caipirinha recipe printed on them.
In Curitiba, I was surprised (but happy!) to find barreado, feijoada and caipirinhas all served at Villa das Artes (see my Restaurant Tips.)