225g unsalted butter, chopped, at room temperature
11/3 cups icing sugar mixture
2 tsps rum essence
21⁄4 cups plain flour, plus extra for dusting
1⁄2 cup cocoa powder
1⁄2 cup Dark Choc Bits
1⁄2 cup raisins, finely chopped
1⁄2 cup Dark Choc Melts
Beat butter, sugar and essence in a small bowl of an electric mixer until light and fluffy. Beat in egg until combined. Transfer to a large bowl of an electric mixer. Add combined sifted flour and cocoa, Choc Bits and raisins. Beat on low speed until just combined.
Turn out dough onto a lightly floured bench. Knead lightly until smooth. Divide in half. Shape portions into 6cm x 20cm long rectangular logs (3.5cm thick). Wrap separately in plastic wrap. Refrigerate for 2 hours, or until firm.
Trim ends of each log. Cut into 1cm-thick slices. Arrange about 3cm apart on two large oven trays lined with baking paper.
Cook in a moderately slow oven (160C), swapping trays halfway through, for 18 minutes, or until firm. Remove from oven. Stand on trays for 5 minutes. Transfer to a wire rack to cool.
Place Dark Choc Melts in a medium, heatproof bowl. Sit bowl over a saucepan of simmering water. Stir until smooth. Remove from heat.
Transfer chocolate to a medium snap-lock bag. Squeeze into one corner. Twist bag and snip tip of corner. Drizzle chocolate over cookies. Stand at room temperature to set.
TIP: Dough logs can be frozen for up to two months. Thaw in the fridge overnight before slicing.