Final answer:
In Un shortened cakes, sugar is added when beating egg whites at the start, while in chiffon cakes, sugar is divided and added to both egg yolks and egg whites during different stages of mixing.
Step-by-step explanation:
When making an Un shortened cake (also known as a sponge cake), sugar is typically added at the beginning of the mixing process. The sugar is beaten with the egg whites until stiff peaks form. This process is crucial as it helps to stabilize the egg whites and incorporate air, giving the sponge cake its characteristic light and spongy texture.
In the case of a chiffon cake, sugar is usually divided into two parts. Part of the sugar is added to the egg yolks, and the other part is added gradually to the egg whites after they have reached soft peaks. The gradual addition of sugar to the egg whites helps to create a stable meringue, which contributes to the chiffon cake's lightness and volume.