In a large bowl, sift all the dry ingredients - 1 kg flour, cinnamon, ginger, allspice, salt, baking soda, cloves and nutmeg. Set aside the 100g of flour.
You will need a stand mixer for this as there is a large amount of dough to handle. You can easily halve the recipe if you wish.
With the paddle attachment on your stand mixer, cream butter and sugar on medium-high speed for about 5 minutes until fluffy and pale in color.
Reduce the speed to medium and add eggs, one at a time, mixing well between additions.
Add molasses and vanilla and mix until well incorporated.
On stir speed (or low speed), add flour and mix until a dough is formed. You may need to use your hands to knead the dough at the end to make sure it's mixed well. Remove the dough from the bowl, and knead it gently a few times to form a smooth ball (dust the work surface with flour if necessary). Add the extra 100g flour only if the dough is too wet, and you require more.
Divide the dough into 4 portions, and flatten each into a disc and wrap in plastic wrap (see photo in post).
Chill all the discs of dough for at least 2 hours in the fridge (I keep it overnight).
For the dusting flour - mix the flour and spices together and use this to dust the surface you will be rolling the cookies on. You can make more of the dusting flour (you will need more) as you need it (optional).
Preheat oven to 325 F/170 C.
Remove one dough disc and then remove the plastic wrap. Place this on a floured (with dusting flour) parchment paper and flour the top of the disc and roll out the dough with a rolling pin (use another parchment paper if the flour is sticking to the rolling pin). Make sure to flip the dough over half way through to smoothly and evenly roll it out. Keep it lightly dusted so that it doesn't stick to the surface.
To ensure that you get an even thickness throughout the dough, use two 5 mm dowels on either side of the dough (or you can use rolling pin rings).
Cut out the shapes of the gingerbread house. 1st portion - walls. 2nd portion - front and back. 3rd and 4th - roof. Use cookie cutters to cut out shapes from the leftover scraps of dough. Cut the windows and doors from the gingerbread house pieces, but do not remove them - this is because the dough expands as it bakes. I prefer to cut them out after they have been baked.
Knead the scraps to form a rough disc and wrap it in plastic wrap. Refrigerate for at least 30 minutes and reuse.
Place the cookies on a cookie tray (lined with parchment paper) with 1 1/2 inches of space between them. Transfer to the freezer for another 10 -15 minutes, or the fridge for 30 minutes.
Bake in the oven.
7 minutes for smaller cookies.
10 - 12 minutes for the walls and front and back.
15 - 18 minutes for the roof. (Longer for larger pieces like the roof or walls). Bake in the oven until the edges JUST start to brown.
Cool the cookies on the tray for about 20 minutes and transfer them to the cooling tray to finish cooling.
Using a sharp knife or craft cutter, cut out the doors and windows of the gingerbread house, while it's still fairly warm on the tray.
I left the larger cookies on the cookie tray to cool down completely.
Use royal icing or melted chocolate to stick the pieces of the house together. If you use royal icing, you will need to leave it to dry for at least 8 hours at room temperature, until it completely hardens up. I keep it for 24 hours.