I have heard Bob speak of viili, and I believe there is also a song about it (from the pen of the irrepressible John Dwyer? Sounds likely). As I understand it, it is a sort of Finnish yogurt. I experimented with various spellings on google and came up with nuthin' (I hadn't tried a double "i"), so I tried "Finnish yogurt" and turned up the following on someone's forum (contributed by a person named John K. Bispala—subject to Bob's corrections:

Viili is a yogurt-like sour milk product, though milder, somewhat nutty, and creamier. It's best made with a viili starter, but can also be made with buttermilk. 1 teaspoon buttermilk or starter, 1-1/2 cups milk, regular or nonfat, I like using whole milk best. Viili would taste even better made from 4% milk, if that were available. You can mix regular vitamin D milk, which is 3%, with half-and-half, which is 10% butterfat, to increase its richness. Put starter or buttermilk at bottom of a very clean dessert bowl. Heat milk to lukewarm, pour over buttermilk. Stir a little. Let stand at room temperature in dark and draftless place one day. The bacteria will thicken it. Do not shake while it is forming or it will become watery. When viili has thickened, chill it. Take a few spoonfuls of the last bowl of viili you eat and use it as starter. Try to include some of the white mold from the top of the villi bowl, since this is the most delicious part and will give your viili more vitamin B. Keep in cold place few days, but not too long. Serve cold with sugar and cinnamon or ginger sprinkled on top, or with berries and sugar, or just sugar, or plain.

Bispala goes on to say,

My dad used to eat viili with my uncle, John Isaacson, who claimed "the viili was no good unless you could stretch it from here to Iron Junction."

Don Firth