Mix the flour, cocoa powder and salt in a bowl. Add the butter and rub together using your hands to form an even, crumbly mixture. Beat the egg white and icing sugar, add and quickly combine to form a dough. Divide the dough in half, shape one of the halves into a roll approx. 4 cm in diameter. Flatten the other half, cover each separately and refrigerate for about an hour.
Chocolate and coconut shortbreads
Combine the chocolate sprinkles and desiccated coconut, roll the dough rolls in it, refrigerate for approx. 30 mins. Cut the dough into slices approx. 5 mm thick, place on a baking tray lined with baking paper.
Chocolate and caramel shortbreads
Roll out the other dough into a 40 cm x 25 cm rectangle. Scatter over the caramel and nuts, roll up, cover and refrigerate for approx. 30 mins. Cut the dough into slices approx. 5 mm thick, place on a baking tray lined with baking paper.
Bake each tray for approx. 10 mins. in the centre of an oven preheated to 200°C. Remove from the oven, allow to cool a little, then leave to cool completely on a rack.