COOKIE DOUGH: In a medium bowl, combine sifted flour and ground almonds, set aside.
In a large bowl, beat together butter, 2 tablespoons vanilla sugar and egg yolk, until smooth.
Gradually add flour mixture to butter mixture, beat until just combined; do not over mix.
Divide the dough into four balls. Roll each ball into a 1-inch thick log. Cover the logs with cling wrap and tie the ends. Refrigerate for at least an hour.
VANILLA SUGAR COATING: In a shallow dish, combine confectioners' sugar and 1/4 cup vanilla sugar for coating the cookies.
Preheat oven to 350 degrees. Line two baking sheets with parchment paper.
On a lightly floured surface, cut the logs into 1/2-inch slices and form into little crescents. Transfer crescents to a prepared baking sheet.
Bake for 8-10 minutes. remove from the oven; cool 1-2 minutes then gently roll the cookies in vanilla sugar while they're still warm, so the sugar will stick. Let the cookies cool completely on a cooling rack. Store in an airtight container in the refrigerator.
HOMEMADE VANILLA SUGAR: Pour granulated sugar to a glass mason jar. Slice the vanilla bean in half, scrape out the seeds with your knife, and add the seeds and bean to the jar. Close the jar and shake well. Do this every day for one week! Voila, you have vanilla sugar!