Preheat oven to 350 degrees F (175 degrees C). Line baking sheets with parchment paper.
Separate the eggs.
Cream the butter or margarine with the sugar. Beat in the egg yolks and vanilla. Stir in the flour and the salt.
Shape the dough into small balls and roll in the slightly beaten egg whites then in the chopped nuts. Press thumb in center of cookie to make an indentation.
Bake at 350 degrees F (175 degrees C) for 7 minutes or until lightly brown. Cool then fill with your favorite frosting or jam.
