Skyr, pronounced "skeer," is the traditional yogurt of Iceland. It is made by incubating skim milk with live active cultures. The whey, the water naturally found in milk, is then strained away to make for a much thicker, creamier, concentrated yogurt. So to make just one cup of skyr, with all that water going out, you need 4 times the amount of milk required to make a regular cup of yogurt. As a result of this process skyr comes out with 2-3 times the protein count of standard yogurt.
Since skyr is fat-free it has been an age old practice to throw a bit of cream back into it for a tad richer touch: generally called rjóma-skyr; or skyr with cream. Delicious! (from Siggi's)