In mixing bowl cream together butter, sugar, salt, egg yolk and vanilla.

Gradually stir in flour blending well. Cover and chill until firm enough to handle.

Work with half of dough at a time, keeping remaining portion refrigerated.

Shape well-rounded teaspoons of dough into balls about the size of marbles, roll in nuts.

Place one inch apart on ungreased cookie sheets, gently pressing thumb in center of each cookie to make a shallow indentation; fill with jelly.

Bake at 350 degrees for 10 to 12 minutes.

Cool on wire rack.