Start by melting the white chocolate and then add about a tbsp worth to the first plank mould.

Scrape it into the grain really well trying to leave no gaps with your bench scraper, straight edge cake scraper or spatula.

Scoop any extra into the next mould and repeat until you have filled the 4 plank mould and 3 plank mould. Leave any excess white in a bowl covered to re-melt to make the last 3 planks you will need.

When this is set (you can pop it in the fridge for 10 mins if you like) then melt the first 800g of dark chocolate and pour into the moulds. Again, use your scraper to level the chocolate and leave this to set - this will likely take several hours but you can leave it overnight if that is easier.

When set, gently unpeel the moulds and then repeat the above procedure to make an additional 2 small planks and a final large one using the remaining chocolate. If you have any dark chocolate left over, pop it into the piping bag, tie the end and leave until you are ready to assemble - this will be the "glue" to stick your planks together. When ready to use it, you can put the bag in a small jug and cover with recently boiled water to re-melt it as long as you don't let water get in the end and haven't snipped the tip off yet!

To assemble: lay three of the smaller planks side by side with the longest edges touching. Use a little melted chocolate to fill the gutter you get by placing the planks together - fill it to the top and leave to set. It should be nice and solid. Repeat with the remaining three small planks.

For the large planks, place two side by side and join with melted chocolate. Once this is completely set solid, you need to cut the larger end pieces to give the shape you see in the pictures.

Mark 10cm up on each of the long sides then 5cm in on the top edge. Use a sharp knife which has been run under hot water and dried, to cut these two corners off. You will be left with a piece of chocolate that resembles the side of a house. You may eat these off cuts!

Next take a 2.5cm round cookie cutter (approximate size) and place in a small dish with some very hot water in. Using an oven glove, take the heated up cookie cutter and slowly, gently but firmly push it until you get a little resistance, about 2 cm down from the top of shortest edge you have just created by trimming the edges off. Wiggle it out carefully and heat it up again so that this time, you should be able to push the hot cutter all the way through the chocolate. Eat this spare piece of chocolate too!

Now put these pieces aside until ready to assemble the cake.