Preheat oven to 180 degrees celsius (fan-forced). Line two baking trays with baking paper and set aside.
Use an electric beater to cream the butter and brown sugar until pale and creamy.
Add the golden syrup and egg yolk and beat until combined.
Stir through the plain flour, mixed spice, ground ginger, bi-carbonate soda and a pinch of salt.
Turn onto a lightly floured board and knead into a ball. Wrap in cling wrap and place into the fridge for 1 hour.
Place the dough between 2 sheets of baking paper and roll out until about 3-4mm thick. Use your choice of cutters (gingerbread man, Christmas tree, stars etc) to cut out shapes.
Place onto the prepared trays (about 4cm apart) and bake for 8-10 minutes or until just lightly golden (do not overcook).
Allow to cool on the trays for 10 minutes before transferring to a wire rack to cool completely.
Once they've completely cooled, decorate with red & green M&Ms and a white icing pen (or white chocolate).
Store in an airtight container at room temperature.