If you're visiting Helsinki and want to eat where the locals eat, go for Tori. Tori is a cosy, laid-back and a bit shabby (in a charming way) place to eat and drink - juice. They don't serve alcohol at all. But on weekends they do serve breakfast throughout the day, which is genius.
The classic dish of Tori is meatballs in Jallu sauce. Juices are delicious, and so are the pastry. The staff is friendly and speaks really good English, and the price level is very affordable. Depending on the number of customers, the kitchen may be slowish - but the atmosphere usually compensates the slight slowness.