For this cake you will need to bake 1 x 20 cm cake and 1 x 24cm cake using the Chocolate Cake Mixes. I prepared all the mixture together and divided it between the 2 cake tins, Please follow the packet instructions for baking times and then allow to cool thoroughly

Prepare the chocolate buttercream Start with softened butter (not melted, but soft). Use an electric beater or cake mixer to beat the butter until it is as white as possible. Then add the cocoa and ⅓ of the icing sugar and beat, add ⅓ of the milk, alternate adding the icing sugar and milk until it has all been added

Take a cake board or large plate, place a blob of buttercream in the centre. Place the larger cake on top.

Ice the top of this cake with chocolate buttercream

Place the second smaller cake on top, you want it to not be in the centre but up against one edge of the larger cake

Ice the entire cake with chocolate buttercream, this does not need to be perfect, it is a construction site remember

Take the honeycomb and roughly crush it with a rolling pin

Place the Rubble toy or construction vehicle on the very top of the cake, add the crushed honeycomb so that it looks like rocks tumbling down the side of the cakes

Use the Kit Kats to create a fence around the bottom of the large cake

I added a ribbon around the fence, this is not necessary

Use a food processor to crumb the TimTam chocolate biscuits

Apply a rough layer of buttercream to the cake board, sprinkle the cookie crumb on top.. Voila- edible dirt!