Ingredients
1 stick plus 2 tablespoons unsalted butter, room temperature
1/2 cup granulated sugar
1/2 teaspoon kosher salt
1 large egg, separated
1 1/2 teaspoons pure vanilla paste, or 1/2 vanilla bean, split and seeds scraped
1 1/4 cups unbleached all-purpose flour
Gold and pink sanding sugar (preferably a combination of fine and coarse)
Preparation
In a stand mixer fitted with paddle attachment, beat butter with granulated sugar and salt on medium speed until light and fluffy, about 2 minutes. Add egg yolk and vanilla; beat to combine. Add flour and beat until a soft dough forms, about 30 seconds. Divide in half; place each half between two sheets of floured parchment and roll out to 1/4-inch thickness. Refrigerate 15 minutes.
Preheat oven to 325°F. Using a cookie cutter, cut dough into 1 1/4-inch rounds. Gather scraps and reroll; refrigerate 15 minutes and cut more rounds. Refrigerate rounds 20 minutes. Brush edges of cookies with egg white; roll in sanding sugar to coat. Arrange on parchment-lined baking sheets, 1 inch apart. (If dough is softening, return to refrigerator 10 minutes.)
Bake, rotating halfway through, until cookies are just golden on bottoms, 15 to 18 minutes. Let cool completely on pans on wire racks. Cookies can be stored in an airtight container at room temperature up to 1 week.
