Icebox Shortbread

Ingredients

• 1 cup (2 sticks) unsalted butter room temperature
• 1 cup confectioner's sugar
• 1 teaspoon vanilla extract
• 1/2 teaspoon salt
• 2 cups all-purpose flour (spooned and leveled), plus more for rolling
• Grated zest of 2 oranges and 1/2 cup dried cranberries optional mix-in
• Grated zest of 2 lemons; coat with 1/4 cup poppy seeds optional mix-in
• Grated zest of 2 limes; coat with 1/4 cup cornmeal optional mix-in
• 1/2 cup chopped dried apricots; coat with 1/2 cup finely chopped pistachios optional mix-in
• 1/2 cup mini chocolate or peanut-butter chips optional mix-in
• 1/4 cup finely chopped candied ginger; coat with 1/4 cup sesame seeds optional mix-in

Instructions

1. 1
   With an electric mixer, beat butter, sugar, vanilla, and salt until smooth. With mixer on low speed, add flour, mixing just until a dough forms. Stir in desired mix-ins.
2. 2
   Divide dough in half; place each half on a piece of floured waxed or parchment paper.
3. 3
   With floured hands, gently roll each into a 1 1/2-inch diameter log. Dividing evenly, sprinkle logs with desired coating if using, rolling log (to help coating adhere) and pressing in gently. Wrap logs tightly in the paper, and refrigerate until firm, 1 to 1 1/2 hours. (To store longer, wrap log and paper tightly with plastic.)
4. 4
   Preheat oven to 350 degrees. Unwrap logs; with a serrated knife, slice dough 3/8 inch thick (if dough crumbles, leave at room temperature 5 to 10 minutes). Arrange slices, about 1 inch apart, on baking sheets.
5. 5
   Bake until lightly golden around the edges, 15 to 20 minutes. Cool on baking sheets 1 to 2 minutes; transfer to a wire rack to cool completely.