On a lightly floured surface, roll out the dough to approx. 4 mm thick. Cut out shapes of your choice, place them on a baking tray lined with baking paper, brush with milk.
Approx. 13 mins. in the centre of an oven preheated to 180°C. Remove from the oven, leave to cool on a cooling rack.
Mix the icing sugar and food colouring with as much egg white as it takes to form a thick icing. Transfer the icing to a piping bag with a smooth nozzle (approx. 2 mm in diameter). Decorate the gingerbread biscuits with the icing, leave to dry.