Good luck! I've shopped for ingredients in Shanghai, and I couldn't even find baking powder or soda at Carrefour. There were many different flours, many of them for noodles or dumpling dough. It was hard to distinguish those over the others. Of course, I don't read Mandarin. That probably would have helped.
Oh man, good luck. I don't know what to tell you! If you can find sugar, baking powder/baking soda, cake or All Purpose flour, and REAL butter (not that crap they sell in Carrefour, but it would work), and powdered sugar, and an oven, you can make a cupcake, and you could make it interesting by adding different flavors. Perhaps something that you don't see in Shanghai very much, like a lime/coconut cupcake.
You could ask around in one of the Metro's bakeries and they could tell you probably; they must use some type of chemical leavening in their cakes.
What flavor do you want?
