I’d consider Soppakeittiö(found in 3 locations in Helsinki) to be a classic in it’s genre. It’s simple really; the menu consists of 3 soups daily, each around 8−10e. Boulaibasse is a standard soup you can get every day which happens to be my favorite along with traditional borscht soup. They also offer some pastry and drinks. You’ll get as much bread as you can eat. Maybe once or twice has the soup been a bit too salty for my taste but besides those occasions has the quality always been good regardless of the restaurant you choose. Restaurants are located in the local indoor market halls. My favorite is the one in Kamppi as it has the most space and a pretty nice view over the local marketplace from the second floor. In the lunchtime it gets really crowded in Wanha kauppahalli in Kaartinkaupunki and sometimes you’ll need to queue to get seated. They also offer take away.