1/2 cup butter or margarine
1-1/2 cups all purpose flour
1/2 cup sugar
2 eggs, separated
1 teaspoon vanilla
1 cup finely chopped walnuts
1/4 to 1/2 cup apricot and/or strawberry jam or preserves

In a large bowl, beat butter with mixer on medium to high speed about 30 seconds or until softened. Add about half of the flour to the butter. Add sugar, egg yolks and vanilla. Beat until thoroughly combined, scraping sides of bowl occasionally. Beat or stir in remaining flour. Cover and chill about 1 hour. Grease a cookie sheet with butter. Shape dough into 1-inch balls. Roll balls in slightly beaten egg whites, then in walnuts. Place 1 inch apart on the cookie sheet. Using your thumb, press an indentation into each cookie. Bake at 375 for 10-12 minutes or until done. Remove cookies from cookie sheet and cool on wire rack. To serve, fill centers with jam or preserves. Makes about 42 cookies.