1. Beat together butter and sugar in a mixer bowl. Add vanilla and egg yolk. Mix well.
2. Mix flour and salt; add to butter mixture and mix well. Cover; refrigerate at least 1 hour.
3. Heat oven to 325 degrees F. Shape dough into 1-inch balls.
4.Beat egg white lightly in a small bowl. Put nuts in another small bowl. Dip each ball into egg white, then roll in nuts. Put balls 1-inch apart on ungreased cookie sheet. Press thumb in the center of each to make an indentation.
5. Bake until light golden, 15 to 18 minutes. Cool on wire racks. Fill indentation with a small amount of raspberry jam.
From: Faye Kuhn, Earlville, Illinois. Chicago Tribune Annual Food Guide Holiday Cookie Contest, December 8, 1988, First Prize Winner.