2 1/2 c. sifted flour
1 tsp. baking soda
1/2 tsp. cream of tartar
1 c. unsalted butter, softened
1 1/4 c. sugar
3 egg yolks
1 tsp. vanilla

Preheat oven to 350 degrees. Grease cookie sheets. Sift together flour, baking soda and cream of tartar on wax paper. Beat butter and sugar in large bowl until fluffy. Beat in egg yolks and vanilla. Gradually add flour mixture in four parts until well blended. Shape into balls, using tablespoons. Place 2 inches apart - do not flatten. Bake at 350 degrees for 12 minutes until lightly golden on edges.