Make Caramel sauce. Put sugar and water in the pan. and heat it and when it become good color, add boiling water and dissolve.
Put caramel sauce in the cake mold (diameter 15cm)

Make pudding.　Warm the milk and sugar until just before boiling. Whisk eggs and add warm milk little by little. Strain mixture, and add vanilla essence and mix well. Put mixture in the cake mold.

Make sponge cake. Melt butter by microwave. Sift flour and cocoa together.

Put egg and sugar in the bowl together and whisk it very fluffy. Add cocoa flour and mix until it is no longer powdery. Mix melting butter.
Put cake mold.

Pour boiling water on the top plate of the oven, place the cake mold on it, and steam it at 160 degrees for 30 minutes.