In a medium mixing bowl, sift the flour, baking powder and spices and mix together. Set aside.
In the bowl of a stand mixer with the paddle attachment fitted, cream together the dairy-free butter, dark brown sugar and golden syrup. Slowly add in the flour mixture and beat until a crumbly dough forms.
Turn the dough out onto a piece of baking paper that has been lightly dusted with flour to prevent the dough from sticking, and with floured hands press the dough into a flat, round disk before using a rolling pin to roll the dough out to about a 5mm thickness. Make sure to flour the rolling pin if the dough is getting too sticky. Place another piece of baking paper over the rolled out dough and place it in the fridge for 30 minutes to 1 hour to chill.
Preheat the oven to 180°C. Remove the dough from the fridge and cut out shapes using a cookie cutter and place them on a large baking tray lined with baking paper. Combine any excess dough and roll out again, continuing to cut out shapes until all of the dough has been used.
Bake the shapes in a preheated oven for about 8-10 minutes or until the edges are starting to turn golden. The middles will still look quite soft. Let the cookies sit on the tray for 5-10 minutes to cool before transferring to a wire rack to cool completely.
Make the icing. Mix together the icing sugar and vanilla with a little water at a time until a thick paste forms. Add the icing to a piping bag with a small round tip fitted and pipe decorations on the cookies. Let the icing set at room temperature overnight to completely harden before stacking and storing the cookies.