Prepare a wok for steaming. You'll notice that I am not using a steamer rack or insert. That is because the steamer rack I have is too high to use in the wok with the cake pan - the wok lid wouldn't fit properly. A 2-inch high tin can - in this case a can of bamboo shoots - with the top and bottom cut out makes a handy substitute. (Be sure to poke holes in the can to allow steam to escape).
Whatever you use, the important thing is to make sure that the cake pan does not touch the sides of the wok and that the wok lid will fit comfortably on the wok during steaming. Fill the wok with boiling water up to a point about 1-inch below the top of the steamer, can, or whatever you are using for a steamer.
Steamed Chinese Sponge Cake Recipe