Combine flour and salt.

Stir well to blend.

Cream butter, brown sugar, egg yolks and vanilla together thoroughly on medium speed of electric mixer.

Add flour to creamed mixture gradually. Mix well.

Shape dough into ¾” balls.

Dip in egg white and then in chopped nuts.

Place on ungreased baking sheets.

Make indentation in centre of each cookie with thumb.

Bake at 300ºF for 5 minutes.

Press centre down again.

Bake 10-15 minutes longer or until set.

Cool and fill centre with jam.