1.Beat butter, sugar, extract and egg in small bowl with electric mixer until light and fluffy. Stir in sifted flour in two batches.
2.Divide dough in half, knead sifted cocoa into one half; knead rind and craisins into the other half. Using ruler, shape each batch of dough into 4.5cm x 4.5cm x 15cm rectangular bars. Wrap each in baking paper; refrigerate 30 minutes.
3.Cut each bar lengthways equally into three slices. Cut each slice lengthways equally into three; you will have nine 1.5cm x 1.5cm x 15cm slices of each dough.
4.Brush each slice of dough with egg white, stack alternate flavours together in threes. Stick three stacks together to recreate the log; repeat with second log. Refrigerate 30 minutes.
5.Preheat oven to 180°C/160°C fan-forced. Grease oven trays; line with baking paper.
6.Using a sharp knife, cut each log into 1cm slices. Place, cut-side up, on oven trays about 3cm apart. Bake about 15 minutes. Stand 5 minutes before lifting onto wire racks to cool.