Sift together flour and soda. In large mixer bowl, beat eggs with electric mixer until light. Gradually beat in powdered sugar; continue beating on high speed about 15 minutes or until mixture resembles soft meringue. Stir in anise oil. Add about 3/4 of the flour mixture and beat on low speed until combined. By hand, stir in the remaining flour mixture. Cover; let stand about 15 minutes. Divide dough into thirds. On lightly floured surface, roll each portion into 8" square. Let stand for 1 minute. Dust a springerle (little horse) mold or rolling pin with additional flour. Press mold on dough hard enough to make a clear design; repeat for the remaining dough (Roll springerle rolling pin on dough, pressing hard enough to make a clear design.) With a sharp knife, cut the rolled cookies apart. Place on a lightly floured surface; Cover with a towel and let stand about 6 hours or overnight. Sprinkle a greased cookie sheet with crushed aniseed. Brush excess flour from cookies. With finger, rub bottom of each cookie lightly with cold water. Place on prepared cookie sheet. Bake in 300 degree oven about 18 minutes or until a light straw color. Remove to wire rack; cool.