Icing Old Fashioned Chocolate Cake

Our answer

Nigella's Old Fashioned Chocolate Cake (from FEAST) is covered with an icing that is a hybrid of a ganache and a buttercream icing. This gives a delicious and fudge-like icing that will remain slightly soft.

When covering a sponge cake with fondant icing (ready-rolled icing) it is usual to cover the cake in a thin layer of buttercream or ganache to give a smooth surface for the fondant to sit on. Otherwise the fondant icing will show up any bumps and dips on the surface and sides of the cake. If using buttercream then it should be a buttercream that sets to form a slight crust. We suspect that the icing for the Old Fashioned Chocolate Cake will probably be slightly too soft for this and also there will be too much icing as you only need a thin layer of buttercream if covering the cake with fondant. We would suggest making a one third quantity of the Old Fashioned Chocolate Cake icing to fill the cake with and then use a regular buttercream, made with icing (confectioner's) sugar, vanilla and butter, to coat the cake. Smooth the top and sides of the coated cake with a palette knife and then leave the cake in a cool place for 4-6 hours to let the icing firm up, before coating with fondant icing. You can refrigerate the cake briefly to speed up the setting of the buttercream, but don't leave it in the fridge for too long as if the cake is too cold when it is covered with fondant then you can get beads of condensation forming on the fondant.