First add the dry yeast and sugar to the lukewarm milk, stir lightly to dissolve the yeast. Cover with kitchen towel and leave aside until it will begin to froth (about 10 -15 minutes). In a small mixing bowl beat the egg whites. In a large mixing bowl combine flour with salt. Add also the yeast mixture, rest of the milk, yogurt and egg whites. Mix well. Stir in cranberries. Use ladle to transfer portions of the batter mixture onto the frying pan filled with generous amount of oil, to cover at least half of the height of the pancakes. Once the pancakes are browned on one side, turn them over and fry some more. Place on the plate lined with paper towels to remove oil excess. Serve while still hot sprinkled with icing sugar.