Preheat oven to 375˚F. Beat butter and sugar in a large bowl until creamy.
Separate eggs. Place whites in a small bowl, lightly beat, and set aside; then beat yolks and vanilla into butter mixture.
In another bowl, stir together flour and salt. Gradually add to butter mixture, blending thoroughly.
Roll dough into balls about 1 inch in diameter. Dip each ball in egg whites, then roll in finely chopped walnuts to coat. Place on covered baking sheets, spacing 1 inch apart.
Make an indentation in the center of each ball, and fill with about 1/4 tsp raspberry jam.
Bake for 12 to 15 minutes or until lightly browned.