16 tablespoons (2 sticks) unsalted butter, softened
1 cup granulated sugar
1 egg yolk
1/2 teaspoon vanilla extract
1 1/2 teaspoons Key lime juice
2 cups all-purpose flour
1/2 teaspoon salt
Key Lime Icing
3/4 cup confectioners sugar' sugar
1 1/2 tablespoons Key lime juice
Butter Cookies: Cream together the butter and sugar until light and fluffy, about 3 minutes, scraping the bowl down as needed. Add the egg yolk, then the vanilla extract and 1 1/2 teaspoons Key lime juice. Blend in the flour.
Transfer the dough to a large piece of plastic wrap and form into a cylinder that is 2 1/4 inches in diameter. Refrigerate for 2 hours or overnight.
Preheat the oven to 350 degrees F. Butter 2 large baking sheets and set aside.
Cut the cookies into 1/4-inch slices. Place the slices on the baking sheets and bake at 350 degrees F for 8 to 10 minutes. Place the baking sheets onto a cooling rack and cool for 5 minutes. Transfer the cookies to the cooling rack.
Key Lime Icing: Combine the confectioners' sugar and 1 1.2 tablespoons Key lime juice in a small bowl. Brush the tops of the cookies with the icing as soon as the cookies are transferred off the baking sheets.
Yields 50 cookies.