As much as I think Chinese birthday cakes are plain sometimes, I am always amazed at how fluffy and light they are! I decided to learn to make the cake base...the fluffy sponge cake. I found a recipe for rolled sponge cake with cream filled center from this Chinese cookbook from Hong Kong, so I used the recipe for the cake part.
Sponge cakes are tricky to make because if you don't whip the egg whites right, the cake will not be fluffy. Also, make sure the cake gets into the oven right away after scrapping it into the baking pan because egg whites in the batter will lose their airy texture if let out for too long. Lastly, the trick to not make the cake collapse is to turn it upside down with the pan during cooling.