Preheat oven to 350 degrees.
Cut butter into 1/2-inch pieces. In a food processor, process all ingredients until mixture begins to form small lumps. Sprinkle mixture into a 13 by 9 by 2-inch baking pan with a metal spatula, pressing evenly onto bottom. Bake shortbread in middle of oven until golden, about 20 minutes.
Recipe courtesy of Gourmet