1.Preheat oven to 180°C/350°F. Grease 20cm x 30cm (8-inch x 12-inch) rectangular cake pan; line base and sides with baking paper, extending paper 5cm (2 inches) above sides.
2.Make cake according to directions on packet; spread mixture into pan. Bake about 30 minutes. Stand cake in pan 5 minutes before turning, top-side up, onto wire rack to cool.
3.Level cake top; turn cake cut-side down. Using picture as a guide, cut clock from cake. Secure cake, cut-side down, on cake board with a little butter cream.
4.To make butter cream, beat the butter (and any flavouring, if using) in a small narrow bowl with an electric mixer until the butter is as white as possible (this will result in a whiter butter cream which will give you better results if colouring it). Gradually beat in half the sifted icing sugar then the milk, then the remaining icing sugar. Beat until the butter cream is smooth and spreadable. Keep scraping down the side of the bowl during beating.
5.Using round cutter as a guide, mark a circle on top of the cake to represent face of clock. Place one-quarter of the butter cream in small bowl; tint pink. Stir combined sifted cocoa and the water into remaining butter cream in medium bowl until combined.
6.Spread pink butter cream evenly over face of clock, continue down body of cake to within 4cm (1½ inches) of cake edges, as pictured. Spread chocolate butter cream evenly over rest of cake. Outline cake with chocolate-covered bullets. Outline pink section with Smarties.
7.Spoon remaining chocolate butter cream into piping bag; pipe numbers on clock face. Cut thin strips of licorice and position on cake to make hands of the clock. Using picture as a guide, use thin strips of licorice and freckles to make the pendulums.
8.To make and decorate mice, cut 2 Smarties in half; push into prunes for ears, secure with a little butter cream, if necessary. Cut thin strips of licorice for tails and thin strips of snake for whiskers; secure to prune with a little butter cream. Position mice on cake.
EQUIPMENT: 20cm x 30cm (8-inch x 12-inch) rectangular cake pan; 25cm x 35cm (10-inch x 14-inch) rectangular cake board; 9cm (3¾-inch) round cutter; small paper piping bag.Note