This is the first of two different plain sponge cake recipes which grandma got from her friends. You can see this one is labelled as Mrs Choa’s recipe.
The method is identical to the Banana Sponge Cake recipe which was one of grandma’s signature dishes. The equal quantities of butter, sugar and flour as well as method in these two recipe are the same as the classic Victoria Sponge Cake. Read more about the history of Victoria Sponge Cake, which is considered by some to an icon of British culture.
From my own experience with the Banana Sponge Cake, it’s very important to do the creaming properly. Cakes require the fat and sugar to be thoroughly beaten until very light and fluffy so don’t be impatient, and be careful to add the egg very gradually to prevent the mixture emulsifying. (Read more about the creaming method here and here.)
I’ve successfully used 375ºF/180ºC for the Banana Sponge Cake, so I wonder why grandma changed the temperature to 425ºF from the original temperature. I also don’t understand the notes which equate 9 eggs to ‘2 Med + 3 small’.