1 stick (1/4 lb.) butter
1/4 c. sugar
1/2 tsp. vanilla
1 lg. egg, separated
1 c. plain flour
1/4 tsp. salt
1 1/4 c. finely chopped nuts (optional)
1/4 c. jam (strawberry or raspberry are good)

Beat butter and sugar together in mixing bowl. Add vanilla and egg yolk. Mix well. Add flour and salt to mixture and mix well. Cover and refrigerate at least 1 hour. Preheat oven to 325°F. Shape dough into 1-inch balls. Beat egg white lightly in a small bowl. Dip each ball into egg white and roll in nuts (if desired). Place 1-inch apart on ungreased cookie sheet. Press thumb in center to make indentation. Bake until golden (15-18 minutes). Fill indentation with jam while still hot.