Mix the flour, sugar, cocoa powder and gingerbread spice in a bowl. Add the honey, stir the sodium bicarbonate into the milk and add to the mixture, mix together and knead to form a soft, smooth dough. Flatten the dough, wrap in cling film and chill for approx. 24 hrs.
Knead the dough thoroughly once again, add the flour and knead in. On a lightly floured surface, roll out the dough to approx. 5 mm thick. Place the template on top of the dough, cut out. Using the remaining dough, cut out shapes (e.g. stars and hearts). Place the gingerbread pieces on two baking trays lined with baking paper.
Approx. 10 mins. per tray in the centre of an oven preheated to 200°C. Remove the smaller shapes, bake the larger pieces for a further 10 mins. Remove from the oven, leave to cool on a cooling rack.
Gently beat the egg white with the lemon juice, add the icing sugar, beat using the whisk on a hand mixer for approx. 5 mins. until you have a thick icing. Transfer the icing to a piping bag, cut off the tip.
To assemble the house
Using icing for glue, stick one long wall to the floor panel, press down gently, hold briefly until both pieces are stuck together. Cover the edge of the short sides and long side with icing, stick to the floor panel as well as the side walls, press gently, hold briefly until both pieces are stuck together.
Repeat these steps with the remaining two walls.
For the roof, insert half a toothpick into each gable end. Cover the edge of the gable with icing. Place the first half of the roof carefully on top of both gable ends and onto the toothpicks, press down gently. Repeat the process with the other half of the roof.
Decorate the house with the remaining icing, Smarties, sweets and gingerbread shapes.