- 1 cup (2 sticks) unsalted butter
- 2 cups all-purpose flour, spooned and leveled
- 1/2 teaspoon fine salt
- 1/2 cup packed dark brown sugar
- 1/4 cup granulated sugar
- 1 tablespoon finely grated orange zest
- 1 1/2 teaspoons pure vanilla extract
- 2 large egg yolks, at room temperature
- 2 tablespoons turbinado sugar
- Make the cookies: In a small pot cook the butter over medium-high heat, stirring frequently, until golden brown, 6 to 7 minutes. Transfer the butter to a small bowl and chill until firm, 1 to 2 hours. Whisk together the flour and salt, in a medium bowl; set aside.
- In a separate bowl, beat the chilled butter, brown sugar, granulated sugar, and orange zest with an electric mixer on medium-high until light and fluffy, 2 to 3 minutes. Add the vanilla and 1 of the egg yolks and beat to combine. Reduce the mixer speed to low and gradually add the flour mixture, mixing just until combined (do not overmix).
- Form the dough into a 1½-inch diameter log. Wrap tightly in plastic wrap and refrigerate until firm, at least 2 hours or up to 3 days. (The dough can be frozen at this point for up to 2 months).
- Heat oven to 350° F. Line two baking sheets with parchment. Unwrap the dough and cut into ½-inch slices with a serrated knife; place on the prepared baking sheets, spacing them 2-inches apart. Brush with the remaining egg yolk and sprinkle with the turbinado sugar.
- Bake until the edges are lightly golden and firm to the touch, 11 to 13 minutes. Cool slightly on the baking sheets, then transfer to a wire rack to cool completely.
- Storage suggestion: Keep the cookies at room temperature in an airtight container for up to 5 days.