Having married into a Finnish family some twenty years ago, and living da U.P. amongst mostly Fins, I learned to make Pannukakku years ago. Learning how to make it was pretty much a condition of marriage. 
(That, plus enduring the stream-fishing adventures with Uncle Carl aka Kala.) Its a staple for alot of folks. And, out of that batter, with some tweeking, you'll get Finnish pancakes- which my FIL excels at making. Birch syrup is amazing. Some friends down the road from me make it, and sell it locally. Not sure if they have a website, but it would be under "Niemela Family Growers". They do fantastic maple syrup, as well.
Another addictive food is Nisu (or Pulla in Finnish). Its a sweet bread containing ample amounts of cardamom. My FIL enjoys it with a light icing; my kids like it slathered with butter. We usually braid it, and that's how you'd find it at most all the stores and bakeries up here. Sometimes, you'll find the Nisu with raisins or sliced almonds..but I never make it that way.
edit: We just celebrated Heikkenpaiva up here, and welcomed the Finnish Consulate General to the festivities. LOTS of Finnish foods in great abundance there were!
