How to Make It
In a food processor, pulse the flour, butter and salt until small pea-size pieces form. Transfer to a medium bowl and add the confectioners’ sugar, egg yolk and vanilla. Using your hands, knead and press the mixture just until a dough forms; divide in half. On a lightly floured surface, roll each dough half into a 12-inch log. Wrap the logs in plastic and refrigerate until firm, about 2 hours.
Line 2 baking sheets with parchment paper. Spread the turbinado sugar on a large plate. Brush the logs with the egg white and roll in the turbinado sugar. Slice crosswise 1/2 inch thick and arrange the slices on the prepared sheets, spacing them 2 inches apart. Freeze for 1 hour.
Preheat the oven to 375°. Bake the cookies for 12 to 14 minutes, shifting the pans from top to bottom and front to back halfway through, until the bottoms are golden. Transfer to racks to cool completely.