I have eaten in those places (because of my guiri friends ;) but if you are asking me where to eat proper catalan food you can't miss Restaurant Pa i Trago (catalan name which means Bread and Drink).
Picture Pa i Trago from TripAdvisor
When you first step in you realize it's not a luxurious restaurant not even modern. It has got a country and simple decoration and you are not going to sit down in a very comfortable chair with a wide table.The menu isn't too large but you can choose from tapas to starters and main dishes. They serve good portions so don't be too brave with food (said by someone like me that eats a lot).
We were 2 people and ordered: 2 tapas, 1 starter and 2 main dishes.
Tapas: we went for Olot's potatoes (I forgot to take a picture of them) and snails with an onion, bacon tomato sauce. We also shared an Esqueixada. This is a salt cod salad that consists of desalted and torn dried and salted cod mixed with vegetables, such as tomatoes, onions, and sometimes pepper. Very typical from the catalan cuisine.
Then, as main dish, I went for a "botifarra amb mongetes". It is a classic Catalan dish of sausage with white beans.
To make all that food go down, we shared a sangria! Oh, it was delicious! plus it was sunny outside so the sangria was very refreshing (although I guess it was way too much for only 2 px!).
I have to admit that after that feast we didn't have room enough for any dessert but, to be honest, they don't have the best desserts menu (note: they are not even homemade!). But it was just enough.
Everything cost 25€ each which was far for that much good food we had! Oh, and if you go there, be sure you order a table in the entrance. They display 3 tables in that room that are separated from the main big dinning room inside. In the entrance you are close to the bar and the kitchen so you see what is really going on in the restaurant. The best is that you can have a talk with the owner and some nice daily diners :)
You can see the owner in the pictures I took him. He event old us some jokes!
*Pictures by me
Restaurant Pa i Trago
Parlament, 41 08015 Barcelona, Spain
+34 934 41 13 20
http://www.restaurantpaitrago.cat/