Sift all of the dry ingredients in a large bowl. Work in the shortening like pie crust. Add buttermilk, eggs, and vanilla. Mix well, mixture will look like pie crust. Let margarine stand at room temperature until soft. Work into the above mixture with your hands. Roll portions of dough to size desired. Cut and roll in sesame seeds. Bake at 350 for 15 minutes. Makes about 20 dozen; 42 cookies per lb. Input: 11/16/91