In a large bowl, whip egg whites until stiff. Beat in the yolks one at a time, beating well after each addition. Stir in the confectioners' sugar, baking powder and anise oil.
Mix in the flour 1 cup at a time, mixing well after each, until dough is fairly stiff. On a lightly floured surface, roll out dough to 1/2 inch thickness. Flour a springerle rolling pin and carefully roll it over the dough, leaving the imprints.
Cut cookies along the lines of the design and place them 1 inch apart on a lightly greased cookie sheet.
Let cookies stand overnight in a cool place to dry.
Preheat the oven to 325 degrees F (165 degrees C).
Bake cookies for 8 to 10 minutes, or until the bottoms are lightly browned.
