1.Preheat oven to 150°C/300°F. Grease and flour 14cm x 21cm (5½-inch x 8½-inch) loaf pan and one hole of a 6-hole (¾ cup/180ml) Texas muffin pan.
2.Make cakes according to directions on packets. Pour ½ cup mixture into muffin pan hole; bake muffin about 30 minutes. Pour remaining mixture into loaf pan; bake about 50 minutes. Stand cakes in pans 5 minutes before turning, top-side up, onto wire rack to cool.
3.Level top of loaf cake. Using a small serrated knife, trim cake, cut-side up, into a rounded shape, slightly pointed at one end.
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.Reserve ½ cup butter cream, tint remaining butter cream blue. Secure loaf cake to cake board with a little blue butter cream. Spread blue butter cream all over cake.
6.To make propeller: melt chocolate; tint grey. Using pattern from pattern sheet, trace propeller shape onto baking paper, then place on tray. Spread chocolate into propeller shape, tap tray on bench; stand at room temperature until chocolate is set. Cut one marshmallow in half; position top half, cut-side down, on propeller for nose cone; secure propeller on plane with a little butter cream.
7.To make cockpit, level top of muffin, turn cut-side down; using a serrated knife, cut into a dome shape. Spread rounded side of muffin with reserved butter cream; secure cockpit on plane with a little butter cream. Position thin strips of licorice for wipers.
8.Using scissors, trim two wafers into large wing shapes. Trim two wafers into smaller wing shapes. Using picture as a guide, position and gently push wings into cake.
9.Trim remaining wafer into shape, rounded at one end, for tail fin. Cut a marshmallow into three slices; position two pieces, cut-side down, onto tail fin. Attach a candy number to the marshmallows with a little butter cream. Gently push tail fin into cake.
EQUIPMENT: 14cm x 21cm (5½-inch x 8½-inch) loaf pan; 6-hole (¾ cup/180ml) Texas muffin pan; 30cm (12-inch) square or round cake board. You need to buy a 80g (2½-ounce)packet of wafers to allow for breakages. The plane and cockpit can be made and covered with butter cream a day ahead. Assemble the plane, particularly the wings, as close to serving as possible.