Preheat oven to 180°C. Grease 23cm x 34cm number four cake pan; line base with baking paper.

Make cakes according to directions on packets. Pour mixture into pan; bake about 50 minutes. Stand cake in pan for 5 minutes before turning, top-side up, onto a wire rack to cool.

To make butter cream, beat butter until white as possible, gradually beat in half the sifted icing sugar then milk, then remaining icing sugar. Beat until smooth.

Using a serrated knife, level cake top. Secure cake to 30cm x 40cm covered cake board with a little butter cream.

Tint butter cream green; spread over top and sides of cake.

Cut licorice to fit length and width of cake, laying two lengths side-by-side, as pictured; press onto cake.

Melt white Melts, spoon into the paper piping bag; pipe road markings down centre of licorice. Attach the red, orange and green Smarties to the candles with melted Melts to form traffic lights; hold in place until Smarties are secure on candles. Position traffic lights on cake.

Using the picture as a guide, decorate cake with Nerds and blue Smarties. Cut tops from Pineapples to resemble bushes; arrange on cake with Racing Cars and the toy trees.