Make batter by adding milk to salt and eggs. Sift in flour gradually until smooth. Heat 7 to 9 inch iron skillet, grease with butter. Pour in enough batter to cover bottom of pan, tilt quickly to cover evenly. Cook on one side until it blisters. Do not turn. Quickly turn out onto towel-covered board.
Filling: Leave cheeses at room temperature. Mix with fork, combine with rest of ingredients. Place heaping tablespoon of filling onto uncooked side of blintz. Fold envelope style. Cook in heavy skillet in small amount of butter until lightly browned on both sides.