Mix 3/4 c. butter and sugars, and beat until light and
     fluffy.  Add egg, vanilla, and salt, and mix well.  Add 
     flour and beat until well mixed.  If necessary, chill 
     about an hour, or until easy to handle.

     Shape dough into 1" balls and place 2" apart on 
     ungreased cookie sheets.  Press down centers of 
     each ball with thumb.

     Bake in preheated 350* oven for 10-12 minutes, or until 
     done.  Remove to wire rack to cool.

     In small bowl, beat 1/4 cup butter and powdered sugar
     until fluffy.  Add rum and beat well.   Spoon about
     1/2 tsp. filling into center of each cookie.  Sprinkle
     with nutmeg.  Chill until filling is firm.

     Makes 4-5 dozen cookies.