Cream butter and sugar.
Add eggs, one at a time, and beat thoroughly after each addition.
Mix in flour and nuts.
Chill thoroughly, preferably overnight.
Shape mixture into bars about 3 inches long, 1 inch wide, and 1/2 inch thick.
Brush with beaten egg.
Arrange on greased cookie sheets.
Bake at 350°F 10 to 15 minutes.
Cool cookies on wire rack.