Decorated Ice-cream Gateau

For the cake: Make the vanilla cake. Once cool, turn out and level the top with a serrated knife. Sit the cake on a inverted cake tin.

For the royal icing: In a bowl, add a few drops of blue food colouring to the royal icing and beat until uniformly coloured.

Spoon one-third of the icing into a piping bag fitted with a fluted nozzle. Use a spatula to cover the cake with a thin layer of the icing. Spread the rest of the icing over the top and sides of the cake. Lift the cake carefully onto a plate.

Pipe small blobs of buttercream around the base of the cake. Chill briefly.

For the ice cream decoration: Heat the cream and liquid glucose in a small saucepan until almost boiling. Place the chocolate in a heatproof bowl and pour over the hot cream.

Leave to stand for one minute. Stir until smooth and leave to cool to 43°C | 110F. Scoop the ice-cream onto the centre of the cake and attach the wafer to it. Pour over the cooled ganache, letting it run to the sides and set.