Preheat the oven to 200℃ (180℃ fan)/400°F/gas mark 6. sift the flour, bicarbonate of soda and spices into a large mixing bowl. Add the butter and rub in until the mixture resembles fine breadcrumbs. Stir in the muscovado sugar.
Beat the treacle, golden syrup and egg together and add to the bowl. Mix to form a smooth dough.
Divide the dough into pieces and roll out to about 7mm (⅓in) thick between two sheets of baking parchment. Chill for 20 minutes. Using the template as a guide cut out the gingerbread house pieces. Chill again.
Bake the biscuits in the centre of the oven for 15 minutes. Remove from the oven and while still hot, cut out the pieces again using the template as a guide. Turn over and return to the oven for 5 minutes.
Allow to cool for a few minutes before transferring to a wire rack to cool completely.
Make the royal icing. Whisk the egg whites in a mixer until frothy. Add the icing sugar and mix on a low speed until combined. Then add the lemon juice, increase the speed and beat well for a minute or two.
If desired, split the mix and add food colouring of your choice. I kept mine white and divided between two bags, one fitted with a plain writing nozzle and the other a small star nozzle.
Cement the walls together with the icing. This is best done on while on the board you are going to serve it on. You may find it easier to pipe your windows before assembling.
Next, pipe a thick line of icing along the top of the walls and place the roof in position. Using a star nozzle pipe a thick line of icing along the ridge of the roof. You may need to prop the roof in place for a few minutes for the icing to go off.
Once the house has set it is a good idea to pipe it into position along the base of the house with a little more icing. Decorate as desired.
Nutrition information is calculated using an online nutrition database - is approximate and is meant as a guideline only and really should have no place on gingerbread house!