After a lot of thinking and research into both cars and car cakes, this is how i did it:
Baked a 5" by 12" by 4" tall loaf cake using a good chocolate Madeira cake recipe that carves well (Alan Silverwood multisize square baking tin is brilliant for getting the size and shape for this sort of model)
The Cake Board Templates-
Note: Each item should be sanitised before coming into contact with food
This is where the planning comes in. For a cake on a platform, it needs to be secured to the cake board below and it needs to be food safe. It also needs to be the correct size/shape and the dowels which will sit behind the tyres need to be the right height off the base and in the right position. We made our own MDF 14" square board and two platforms for the car to sit on (one for the board and one to work on while carving the cake). Everything was covered in food safe paper covered foil and attached to the MDF with non-toxic glue stick.
The 'working' cake platform with dowels attached to bottom at the correct height for the model (only the top and sides need covering, the base will not be in contact with the cake):
This shows covering the base cake board, a smoother was used on the top side to give a good finish.
Next dowels the car position was marked on the cake board with a food safe pen and the dowels were attached and covered.
Let the decorating commence!-
It was now time to work on the cake board. It was covered in grey sugarpaste and textured with the back of an unused and sanitised scouring side of a washing up sponge. The car platform for the board was then attached and re-covered.
The cake was put on its working platform and carved using accurate templates of an M3. Tooth pics are very handy as guiding posts when carving as you can see but make sure they are all removed and accounted for.
The cake was split once and then filled and crumb coated with buttercream. I chill my cakes down before putting on the sugarpaste. Some people always do this and some never. It has always worked for me. The car was moved to the final platform which had some buttercream on it to help adhere. One black layer of sugarpaste was applied and then the car was left to dry overnight (this drying time is important for the next bit).
Next day the car was covered in red mexican modelling paste. The properties of this modelling paste work the best for me in this situation. Its flexible, can be rolled thinner than sugarpaste and holds its shape. The car was 'edible glued' all over except for the windows which where cut out afterwards using a scalpel and a steady hand. If the black layer was not dry it would be impossible to tell when to stop cutting throught the red layer of paste. I looked at all the different ways you can do car windows and this method looks the best, which is why the top coat of paste needs to be rolled as thin as you can (e.g. 2-3mm). The wheels were also made from black modelling paste ans stuck on with edible glue.
I left the cake overnight again to form before adding all the final embellishment's and detail work. The wing mirrors of the car were inserted in using dried spaghetti and the sugar model is supported with a pastillage sugar stick internally and dried spaghetti. These items should be removed before the cake is consumed.
Here's a link to a video of the cake:
Check out my website if you want to see more cake pictures:
I hope this has been interesting : )