Can I replace vegetable shortening with extra butter for the Vanilla Layer Cake with Ermine Icing?
Nigella's Vanilla Layer Cake With Ermine Icing (from AT MY TABLE) has a vanilla sponge that is light and soft, with a fine crumb. This ethereal texture is achieved by using a combination of butter (for flavour) and vegetable shortening (for texture). Shortening is completely made of fat, unlike butter (which is 80% fat plus water and milk solids) and this helps to stop too much gluten development in the flour used for the cake batter.
Our preference is to use vegetable shortening. It may be possible to use refined coconut oil instead, but you need to make sure that it is exactly at the right cool room temperature so that it is not too solid and also has not turned into liquid. We would also suggest using refined coconut oil as it has a neutral taste, unrefined coconut oil will make the cake taste slightly of coconut. If you do have to use all butter for the sponge then it will have a slightly heavier, slightly tougher texture.