Why Did My Old Fashioned Chocolate Cake Frosting Turn Runny?

Our answer

Nigella's Old Fashioned Chocolate Cake (from FEAST) is a popular chocolate layer cake. The sponge layers are sandwiched and coated with a fudgy chocolate frosting. If the cake seemed dry or crumbly there are two possible reasons. One is that the cake had been baked for too long and become dry. It should be baked until the sponge is just firm to the touch and a cake tester comes out clean and Nigella does suggest checking on the cake fairly early on during the baking, to try and prevent over baking. It is also possible that the cake batter ingredients were over mixed in the food processor. You should mix only until the ingredients are just combined.

Sponges need to cool fully before they are frosted and if the cake was crumbling it may still have been too warm to move about. So make sure that the cake layers are completely cold before moving the cake to a cake plate. If the cake was too warm then this would also cause the frosting to become more liquid and runny as it went on to the cake. The other reason the frosting may be too runny is if the chocolate had become overheated and split (in which case the frosting could look a little oily as well) or if the chocolate and butter mixture had not cooled enough before being added to the other ingredients. If the frosting is too warm then you can usually put the bowl into the fridge and chill the mixture until it firms up. But keep a close eye on it and stir it every 3-4 minutes until the consistency is right, otherwise it can become too solid.