Stir together flour, sugar, and vanilla beans in a large bowl. Blend in cold butter until all butters is small bits. Beat in egg yolks. Knead dough with hands until smooth.
Roll dough into a tube shape and cut into 6 equal pieces.
Roll out each piece of dough into breadstick shape. Place plastic over it and refrigerator for at least 2 hours.
Cut each "breadstick" into 6 equal pieces and form into crescent shape cookies on baking sheet.
Bake at 350 °F for 8 -10 minutes.
While cookies are warm, sift with powdered sugar and let cool on wire rack.