Makes 6 dozen
Cream butter and sugar.
Whip egg whites with the salt until stiff. Fold into butter mixture.
Sift flour and add slowly to the butter mixture.
Roll dough very thin on a lightly floured board and cut into rounds with a cookie cutter. Place on lightly greased cookie sheets and chill anywhere from 1 hour to overnight in the refrigerator.
Bake in a preheated 375° oven 10 to 12 minutes, or until a golden brown.
Remove from oven. Spread half of the cookies with a dab of jam or preserves. Cover with the other half. Make sure the oven is turned off and return the cookies to the warm oven to dry.