Fruitcake Shortbread

Basic Shortbread Cookie Dough In stand mixer using paddle attachment, or in bowl using wooden spoon, beat together butter, icing sugar and vanilla until light and fluffy; stir in flour just until combined. Divide dough in half; press into discs. Wrap each in plastic wrap; refrigerate until firm but still soft enough to roll out, about 30 minutes. Fruitcake Knead dough with glazed fruit until combined; using hands, shape into 2 squares. Place each on large piece of plastic wrap; loosely pull up over dough. Using plastic, press and shape each half into 7-inch (18 cm) square, smoothing edges. Refrigerate until firm, about 45 minutes. Cut each square into 4 strips; cut each crosswise into seven 1-inch (2.5 cm) thick slices. Arrange, 1 inch (2.5 cm) apart, on parchment paper–lined rimless baking sheets. Bake, 1 sheet at a time, in 325 F (160 C) oven until edges are light golden, 22 to 24 minutes. Let cool on pans on racks for 5 minutes. Meanwhile, whisk icing sugar with rum until smooth. Transfer warm cookies to racks; brush glaze over tops. Let cool completely. Make-ahead: Layer between waxed paper in airtight container and store for up to 1 week or freeze for up to 2 weeks.