1.Preheat oven to 180°C/350°F. Grease a 23cm x 34cm (9¼-inch x 13½-inch) number 4 cake pan; line base with baking paper.
2.Make cakes according to directions on packets; pour mixture into pan. Bake for about 50 minutes. Stand cake in pan for 5 minutes before turning, top-side up, onto a wire rack to cool.
3.Meanwhile, to make butter cream, beat butter in a small bowl with an electric mixer until as white as possible. Gradually beat in half the sifted icing sugar, milk then remaining icing sugar. Tint butter cream blue.
4.Using a serrated knife, level cake top; secure cake to a 25cm x 40cm (10-inch x 16-inch) rectangular cake board with a little butter cream.
5.Spread butter cream all over cake.
6.Using a sharp pair of scissors, trim each fruit stick to fit across the cake. Using the picture as a guide, decorate cake with fruit sticks.
Use a gluten-free packet cake mix for this recipe, if you like. Just make sure the ingredients for the butter cream and the decorations are also gluten-free. Number 4 cake pans can be hired from cake decorating suppliers.Note