Plan is a big square chocolate cake, covered in green icing for grass (solid icing or buttercream?). Then to out Tarmac down using the roll out icing in black, pipe markings on it and buy little jelly racing cars.
Does this sound like it will work or am I making some huge error? Or do you have better ideas because I would LOVE to hear them.
Sounds fine- but why not have a go at modelling little racing cars out of icing? You can buy a packet of 5 different colours (including black for tyres) from any supermarket, and I absolutely promise it's much, much easier than you think. And fun. and addictive
If you google racing car cake images you'll find loads of inspiration.
You can use roll out icing (fondant, sugarpaste, ready to roll icing are all the same thing) coloured green, or you could use buttercream coloured - if you want to go the whole hog give yourself hand cramps you could pipe buttercream through a grass nozzle. Personally when I do grass I use green sugarpaste and do a border round of jagged cut sugarpaste in a slightly different green to look like grass - I'll see if I can find a pic.
Oh that looks great LizzieMint I need to keep it simple so the grass effect you've done there I could probably make an attempt at (in simple form). And thank you for the icing advice, I had no idea what to get!