Open the cake box, remove enclosed frosting sachet and reserve for another use. Place the cake mix in a bowl and stir in the ginger and cinnamon. Add the butter, black treacle and eggs and beat with a wooden spoon to make a firm dough. Roll out the dough between 2 large sheets of baking paper to 7mm thickness (about 30cm square). Slide onto large baking sheet and chill in the fridge for 30 minutes.
Preheat the oven to 180°C (160°C fan forced). Line 2 large baking sheets with baking paper.
Peel off the top sheet of paper from the dough and using small star and heart shaped cutters (each about 5cm) stamp out 10 stars and 10 hearts. Place well spaced on the baking sheets. Gather the remaining dough into a ball then divide into 10 pieces, roll and flatten into 5cm diameter rounds. Place on the baking sheets.
Bake for 11-13 minutes until pale golden and set. Leave on the trays for 5 minutes then transfer to a wire rack and leave to cool completely.
Place the chocolate frosting in a microwave proof bowl and heat on High for 20-30 seconds or until melted. Stir until smooth. Dip half of each cookie into the frosting to coat (See Tip) and place on a wire rack. Chill in the fridge for 15 minutes until set.
Place the vanilla frosting in a microwave-proof bowl and heat on high for 5 seconds until melted. Stir until smooth then spoon into a disposable piping bag fitted with a fine writing nozzle. Pipe zig-zag lines of frosting over each cookie. Leave to set. Store in an airtight container in a cool place for up to 2 days.