1. Mix all the ingredients in a bowl. Beat with the mixer on low speed first, then increase the speed and beat for about 10 minutes until thick with a trace.
2. Heat the steamer.
3. Pour the mixture into the mold that has been lined with paper cups until it is full. Shake it before putting it in the steamer.
4. Steam the cake for about 25 minutes. During the steaming process do not open the steamer lid.
5. After the cake is cooked, let it cool and then remove it from the mold. Lift and serve.
Good luck and hope you like this chocolate sponge cake!