Final answer:
The two forms of sponge cake refer to different methods used to create their light and airy texture, which is achieved through the batter or foaming methods of mixing and the chemical reactions for leavening during baking.
Step-by-step explanation:
The two forms of sponge cake mentioned in the question likely refer to the different methods used to achieve the cake's fluffy texture. The leavening of sponge cakes typically involves entrapping air through the beating of eggs. Sponges can be made using the 'batter' method, where eggs and sugar are whipped together until thick and then folded into the flour, or by the 'foaming' method, where the eggs are separated, and both the yolks and whites are beaten individually with sugar before being combined. Both methods rely on the incorporation of air and proper mixing techniques to ensure the cake rises properly, producing its characteristic light texture.
While baking, the chemical reactions involving an acidic ingredient and sodium bicarbonate produce carbon dioxide gas at high temperatures, contributing to the fluffiness of the cake as described. Various icing and decorations can be applied to sponge cakes post-baking, such as a buttercream frosting, which adds to the cake's overall appeal and flavor.