In a large bowl, stir together sugar and oil. Add 1/2 cup of the buttermilk, the egg yolks, and vanilla. Whisk until batter is smooth. Add the remaining 1/4 cup buttermilk and the baking soda; stir just until combined. Stir together 1 cup of the flour and the baking powder; add to buttermilk mixture. Whisk until smooth. Gradually add the remaining flour, stirring until well mixed. Cover and chill dough for 4 to 24 hours.
Preheat oven to 450 degrees F. On a lightly floured surface, drop 1 rounded tablespoon of the dough; roll into a 9- to 10-inch-long rope. About 1 inch from ends, cross one end of the rope over the other end of the rope to form an oval. Lift ends across to opposite side of circle; press to seal. Repeat with remaining dough. Place cookies about 1 inch apart on ungreased cookie sheet.
Bake about 6 minutes or just until starting to brown. Remove from cookie sheet and place on a clean kitchen towel; cover with another clean kitchen towel. Cool completely. To serve, sprinkle tops of cookies with powdered sugar.
Note; You can use other flavors of extract, such as almond, lemon, orange, anise, whatever you like! This is the basic recipe, so play with it!