12 tablespoons unsalted butter -- (1 1/2 sticks) room temperature
1 cup confectioners' sugar
Grated zest of 2 limes
2 tablespoons freshly squeezed lime juice
1 tablespoon pure vanilla extract
1 3/4 cups plus 2 tablespoons all-purpose flour
2 tablespoons cornstarch
1/4 teaspoon salt
1. In the bowl of an electric mixer fitted with the whisk attachment, cream butter and 1/3 cup sugar until fluffy.
Add lime zest, juice, and vanilla; beat until fluffy.
2. In a medium bowl, whisk together flour, cornstarch, and salt.
Add to butter mixture, and beat on low speed until combined.
3. Between two 8-by-12-inch pieces of parchment paper, roll dough into two 1 1/4-inch-diameter logs.
Chill at least 1 hour.
4. Heat oven to 350°.
Line two baking sheets with parchment.
Place remaining 2/3 cup sugar in a resealable plastic bag.
Remove parchment from logs; slice dough into 1/8-inch-thick rounds.
Place rounds on baking sheets, spaced 1 inch apart.
5. Bake cookies until barely golden, about 15 minutes.
Transfer cookies to a wire rack to cool slightly, 8 to 10 minutes.
While still warm, place cookies in the sugar-filled bag; toss to coat.
Bake or freeze remaining dough.
Store baked cookies in an airtight container for up to 2 weeks.