In medium bowl, combine flour, walnuts and salt. In large bowl, beat butter and sugar with electric mixer until light and fluffy. Add egg and vanilla; mix well. Gradually add flour mixture; mix well. Shape dough into 1-inch balls. Place on cookie sheet and make indentation in ball.
Bake 12-15 minutes or until edges are golden brown. Remove cookies from cookie sheet to cooling grid; immediately top with candy, jam or nut. Cool completely.