In a large bowl, beat the butter and dark cane sugar until creamy. Mix in the baking soda, salt, ginger, mixed spice and cinnamon. Mix in the treacle and warm water then slowly mix in the flour. Add a little extra flour if the mixture is too moist to roll out. Cover with plastic wrap and chill in the fridge for at least 3 hours. The mixture can be stored in the fridge for up to 5 days.
Preheat oven to 180°C. Cover two oven trays with baking paper or spray with non stick baking spray.
Divide the dough into 4. Taking one quarter at a time, roll out to 1 cm thickness on a floured bench or board. Cut out the gingerbread people shapes using a cookie cutter. Use a wide spatula to transfer to the prepared trays. Bake for 12 – 15 minutes until firm and dark gingerbread brown. Cool for 2 minutes on the tray then remove to cool completely on a wire rack. When cold, ice with Royal icing using a piping bag to outline details.
Place all ingredients in a large bowl and beat with an electric beater until fluffy, thick and shiny. Spoon into a piping bag or you can use a small ziplock plastic bag with a small hole cut out of the corner. Pipe on faces and clothing details.