Cream the yeast with a little milk, then add the remaining milk, the egg yolks and sour cream.
Sift the flour and salt into a bowl and add the yeast mixture. Stir to make a thick batter. Leave for at least 1 hour in a warm place. The batter should now look bubbly. Stir well. Just before cooking, whisk the egg whites until stiff and fold them into the batter.
Heat a little oil in the pan and pour off any excess. Then pour in a tablespoon of batter. Turn the pancake over when it shows bubbles on the top side. Cook lots. One bliny is never enough.