If wanted to make a 9-inch Old Fashioned Chocolate Cake would I have to change the recipe?
Nigella's Old Fashioned Chocolate Cake (from FEAST is a 20cm/8-inch chocolate layer cake. Unfortunately scaling cakes up can be tricky and we have not tried the cake in a larger form. The current recipe could be baked in 23cm/9-inch pans but the cake layers will be much skinnier and the baking time will be shorter. We suggest that you start checking the cake 5 minutes before the end of the recommended cooking time.
If the layers are too skinny then you could make a third layer using half of the recipe quantities and make a three layer cake. To layer and frost a three layer cake cake you will need extra frosting, so we would suggest that you make 1.5 times the quantity of the icing in the recipe.