1.Preheat oven to 180°C; grease and line two deep 20cm-round cake pans. Make cake according to directions on packet, divide mixture between pans; bake in moderate oven about 40 minutes. Stand cakes in pans 5 minutes; turn onto wire racks to cool. Using serrated knife, level cake tops so cakes are the same height.
2.Cut one cake in half; cut one of the halves in half again, as shown. Trim and discard a 2cm slice from each of the two cake quarters.
3.Place whole cake on board, cut-side down; sit half-cake, on its side, across centre of whole cake. Place trimmed cake quarters opposite each other on either side of half-cake. Trim and discard about 1cm from rollette, position on top of crown; secure with skewer. Discard remaining cake.
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.Tint butter cream with burgundy colouring; spread all over crown.
6.Decorate cake with boiled lollies, lollipops and cachous. Bend 15cm chenille sticks to form semi-circles; position gently into top of crown. Bend 30cm chenille sticks to form semi-circles; position around side of crown.