As this cake is very tall, separate top cakes before cutting to serve. Use any coloured fondant to make the stars – but you can’t tint white fondant black, as the colour will end up grey.
100g black ready-to-roll icing
4 x 440g packets golden buttercake mix
Silver star sprinkles, red ribbon and playing cards, to decorate
400g unsalted butter, chopped, at room temperature
3 1⁄2 cups icing sugar mixture
Violet food colouring paste, to tint
Knead icing on a clean bench until smooth. Roll out between two sheets of baking paper until 5mm thick. Using a 5.5cm star cutter, cut out ve stars. Using a 3cm star cutter, cut out the middle from each. Reserve scraps for another use. Brush all the stars with water. Decorate with sprinkles. Stand at room temperature for 4 hours, or overnight, to dry.
2 Grease two 20cm round x 9.5cm deep cake pans and a 24cm round cake pan. Line the bases and sides with baking paper, extending the paper 5cm above the pan edges.
3 Prepare cake mixes, one at a time, according to packet directions. Place 1 1⁄2 cups of batter in the 24cm pan. Divide remaining batter evenly between other pans.
4 Cook 24cm pan in a moderately slow oven (160C) for about 20 minutes, or until cake is cooked when tested. Stand for 5 minutes. Turn out onto a wire rack to cool.
5 Cook remaining pans in same oven for about 1 hour, 10 minutes, or until cakes are cooked when tested. Stand for 10 minutes. Turn out onto wire racks to cool. Reserve icing sachets for another use.
6 To make frosting, beat butter in a large bowl of an electric mixer until fluffy. Beat in sugar, 1⁄2 cup at a time, until smooth. Tint purple.
7 Invert 24cm cake onto a cake board. Spread evenly with some of the frosting. Refrigerate until firm. Trim tops of remaining cakes to sit at. Sandwich together with 1⁄3 cup of the frosting. Position on top of the large cake. Spread evenly with remaining frosting.
8 Decorate with stars, ribbon and cards.