All you'll need is the base cake like TJ's Chantilly cream vanilla bean variety, some jam (which has a better texture than jelly for this use), and poured fondant (rolled sheets will be much ...

Roll the light blue fondant out onto a surface dusted with cornflour, to around 5mm thick, or until you have a sheet big enough to cover the cake. Trim off any excess using a sharp knife.

Place a large cooling rack over a sheet of newspaper. Dip the chilled cakes into the lilac fondant to cover the sponges. Set the fondants onto the rack to drip dry. Place the remaining buttercream ...