Vanilla Bean Thins

Preparation

1. Make vanilla sugar:

   Step 1

   Scrape vanilla seeds from pod with tip of a knife into confectioners sugar. Halve pods crosswise and bury in sugar. Cover tightly and let stand at least 24 hours and up to 1 month.

2. Make cookies:

   Step 2

   Discard pods and transfer vanilla sugar to a food processor. Add flour, salt, and baking powder and pulse to combine. Add butter and pulse just until mixture is in pea-size lumps. Add yolk and pulse just until a dough forms. Gather dough into 2 balls, then flatten into 2 (5-inch) disks and chill, each disk wrapped well in plastic wrap, until firm, at least 1 hour.

   Step 3

   Preheat oven to 325°F.

   Step 4

   Roll out 1 disk (keep the other chilled) to less than 1/8 inch thick on a lightly floured surface with a floured rolling pin. Cut out shapes with floured cookie cutter and chill scraps. Arrange cookies 1/2 inch apart on a buttered large baking sheet. Make more cookies with remaining dough, rerolling scraps (but only once).

   Step 5

   Bake cookies in batches in middle of oven until edges are pale golden, 10 to 15 minutes. Transfer to a rack to cool.