METHOD

1. Preheat oven to 160°C (325°F). Place the flour, baking powder, cocoa, sugar, eggs, milk, and vanilla in a large bowl and, using a hand-held mixer, whisk until combined. Gradually add the butter and whisk until well combined. Divide the mixture between a lightly greased 18cm-round tin and 
a 28cm-round tin lined with non-stick baking paper to come 
¾ of the way up the sides of each tin. Bake the 18cm cake for 
1 hour 35 minutes–1 hour 45 minutes and the 28cm cake for 
2 hours 10 minutes–2 hours 20 minutes or until cooked when tested with a skewer. Cool cakes in tins for 10 minutes before turning out onto wire racks to cool completely.
   
2. To make the chocolate butter icing, place the butter in an electric mixer and beat for 6–8 minutes or until pale and creamy. Add the icing sugar, cocoa and vanilla and beat for a further 10–15 minutes or until light and fluffy.
   
3. To assemble, trim the tops of the cakes and discard. Place the 28cm cake on a cake board and top with the 18cm cake. Using a spoon, scoop out some cake from the top cake to create 
a ‘construction’ hole. Place the crumbs in a bowl and set aside. Using a palette knife, ice the two cakes with the chocolate butter icing, leaving the hole uncovered. 
   
4. Knead the black fondant on a clean surface until pliable. Roll out between 2 sheets of non-stick baking paper to 3mm-thick. Using a 26cm-round plate cut a circle from the black fondant. 
Lay a 23cm-plate over this piece and cut around it to create a circular road, reserving the middle. Place this around the top of the 28cm cake. Knead the white fondant on a clean surface until pliable. Roll out between 2 sheets of non-stick baking paper to 3mm-thick. Cut out 32 x 1cm-long pieces for the ‘median strip’. Brush the base of 18 pieces with water and make the road.  
   
5. To create the ramp, make an incision through the 28cm cake on a 45-degree angle. Cut straight down vertically using the smaller cake as a guide. Pull out the wedge of cake and discard 
to create the ramp. Now cut a straight line across the bigger cake using the first cut as a guide to open up the face of the ramp. 
   
6. Knead the remaining black fondant on a clean surface until pliable. Roll out between 2 sheets of non-stick baking paper to 3mm-thick. Cut a 3cm x 38cm piece of road. Place down the ramp and wrap around the base of the cake. Brush the base of the remaining white lines with water and press onto the road. 
   
7. Sprinkle the reserved cake crumbs on top of the cake and along the base of the cake to complete the construction zone. Place honeycomb around the cake to make ‘boulders’. Arrange the cars and toy pieces around the cake to finish. Serves 12–14.

+ Find coloured fondant icing at specialty cake stores.