Makes 6 dozen
Cream butter and vanilla until soft. Add sugar slowly. Beat in egg yolks one at a time. Add flour slowly, blending well after each addition.
Fill a cookie press about 2/3 full of dough and press out cookies in "S" shapes (or in any desired shapes) on greased and lightly floured baking sheets.
Bake in a preheated 350° oven 12 to 14 minutes, or until golden yellow on edges. Watch the cookies while they bake because they scorch easily.